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Providing Support Around Th« World 

JJi kVv 



Issue Number 70 November/December 1994 USS4.00 

Small System Support 

PC/XT Corner: Stepper Motors 

Z-System Corner II 

The European Beat 

Real Computing 

Support Groups 

Dr. S-100 

Multiprocessing for the Impoverished Part 5 

Centerfold - Jupiter ACE 

The Computer Corner 

ISSN # 0748-9331 TCJ - For Having Fun With Any Computer! 

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The Computer Journal 


Art Carlson 


Bill D. Kibler 

Technical Consultant 

Chris McEwen 

Contributing Editors 

Herb Johnson 

Charles Stafford 

Brad Rodriguez 

Ronald W. Anderson 

Helmut Jungkunz 

Ron Mitchell 

Dave Baldwin 

Frank Sergeant 

JW Weaver 

Richard Rodman 

Jay Sage 

Tilmann Reh 

The Computer Journal is pub- 
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The Computer Journal 

Issue Number 70 November/December 1994 

Registered Trademarks 

It is easy to get in the habit of using company 
trademarks as generic terms, but these trademarl<s are 
the property of the respective companies. It is important 
to acknowledge these trademarks as their property to 
avoid their losing the rights and the term becoming pub- 
lic property. The following frequently used trademarks 
are acknowledged, and we apologize for any we have 

Apple II, II+, He, He, Lisa, Macintosh, ProDos; 
Apple Computer Company CPIM, DDT, ASM, STAT, 
PIP; Digital Research. DateStamper, BackGrounder ii, 
Dos Disk; Plu*Perfect Systems. Clipper, Nantucket; 
Nantucket, Inc. dBase, dBASE II, dBASE III, dBASE III 
Plus, dBASE IV; Ashton-Tate, Inc. MBASIC, MS-DOS, 
Windows, Word; Microsoft, WordStar; MicroPro Inter- 
national. IBM-PC, XT, and AT, PC-DOS; IBM Corpora- 
tion. Z80, Z280; Zilog Corporation. Turbo Pascal, Turbo 
C, Paradox; Borland International. HD64180; Hitachi 
America, Ltd. SB180; Micromint, Inc. 

Where these and other terms are used in The 
Computer Journal, they are acknowledged to be the 
property of the respective companies even if not specifi- 
cally acknowledged in each occurrence. 

Editor's Comments 2 

Reader to Reader 3 

Special Review of Gary Kildall's work. 

Z-System Corner II 13 

Intro to CP/M and Z-System, part 3. 
By Ron Mitchell. 

Dr. S-100 17 

Pre-Winter Mall Bag. 
By Herb R. Johnson. 

European Beat 21 

Two articles of interest. 
By Helmut Jungkunz. 

Center Fold 25 

Jupiter ACE. 

PC/XT Corner 29 

Stepper Motors and Forth. 
By Guest: V. Henry Vinerts. 

Real Computing 32 

CD-ROMs and nev^s. 
By Rick Rodman. 

Small System Support 34 

6809 assembly language tutorial. 
By Ronald W. Anderson. 

Multiprocessing for the Impoverished 38 

Part 5: Serial I/O. 
By Brad Rodriguez. 

Support Groups for the Classics 46 

Support groups directory. 

The Computer Corner 50 

By Bill Kibler. 


Welcome to issue number 70 and the 
end of 1994. We finish this year with a 
collection of letters and projects. 

Our Reader to Reader starts out with a 
look at some (^Gaiy Kildall's early work. 
All this is from the machine of 
Emmanuel Roche. He retyped this infor- 
mation so we could understand our loss 
after Gary's death. Since most is copy- 
righted, I have extracted what I hope 
gives you a desire to research his work 
in greater detail. Having read the entire 
material, I can see too that he was not 
only a pivotal person in the industry, but 
very honest and concerned more about 
the user than the bank account. We will 
miss him. 

For those wanting to do more with 
Palmtech's IDE inter&ce, a letter about 
their single chip controller used on the 
Z180 single board computer is also in 
Reader to Reader. And yes it is not all 
specials, I answer s(Hne burning ques- 
tioas fixxn you as well. 

R(m Mitchell continues his walk through 
CP/M and ZCPR. This time we continue 
the discussion of the basic structure of 
CP/M and comment on past and present 
siq^rt resources for Z-System. 

Dr. S-100, or Herb Johnson has plenty 
of letters to reqwnd to as he recounts his 
collecting methods. He ends his corre- 
spondence with a short line on PDP-1 1? 
Now don't seem so surprised, 1 have 
heard fit>m several collectors who have 
the old machines iq) and nmning in their 
garages. How's that for enjoying the past! 

We jump the ocean to hear from Helmut 
Jungkunz, who can be contacted on 
GEnie CP/M roundtable at 4PM EST 
first and third Sundays. I edited together 
a couple of his pieces of work, which 
both give you a better idea of the Euro- 
pean Beat Now Helmut has just had a 
baby and our congratulations or com- 
miserations go out to him, but since I 

know his time will be shorter to spend on 
us, might one of you other Europeans 
like to help him out and contribute to 
TCJl I know Forth is pq)ular in En- 
gland and Russia, but what is happen- 
ing? Got any information you might like 
to share. Drop me or Helmut some mail 
(postal or e-mail), we sure want to hear 
from you. 

Taking up the center of the magazine 
this month is the Jupiter Ace. I wanted to 
follow the ZX81 with this, but trying to 
find other information, and my job too, 
kept getting in the way. So ready or not, 
chedc this simple Z80 based system out. 
I also take this time to start explaining a 
little fimdamental TTL design to help 
those non-logic users along. 

Stq)ping along to the guest in the house, 
we hear fix)m V. Henry Vinerts about his 
steH)er motor project. Hemy took Frank 
Sergeant's stepper motor circuit and 
made it work. So in Franks' place is 
Henry and his Forth based Etch-A- 

For those using CD-ROMs and 32 bit 
machines, Rick Rodman has a few short 
words. From 32 bits to 8, we jump next 
to Ronald Anderson and more on his 
6809 assembler teachings. Now Ron is a 
pretty good teacher, so pay attention here 
if you want to do assembly. Assembly 
yes, 6809 no, you say? I must remind you 
that once you fully understand assembly 
on any chip, moving to others is very 
easy. So here is that chance to get a good 
start working with real computer pro- 

The last feature this time is Part 5 of the 
"Scroungemaster 11." Brad Rodriguez 
fills us in on some of the last stages of 
this project and explains the serial 1/0 
used inside his system. It seems we should 
be hearing from users soon as Brad has 

made and sold most of his first run of 

Since 1 am the editor and been writing 
for TCJ forever, I guess my Computer 
Comer column is rather anticlimactic. 
That is the problem with nmning things, 
I am the last word. Those final words in 
fact are on two items that came in the 
mail bag. Sometimes real goodies come 
in small packages. 

Next Time 

I have lots of articles sitting in my to do 
pile. What's in 71? Well more letters, J. 
G. Owens and his 8048 emulator, Walter 
J. Rottenkolber and one of his many 
great articles waiting to see the top of 
the pile. Space permitting 1 may slip in 
a word on power supplies, an XT inter- 
face or two, and 805 1 development pack- 
ages. Of course the regulars like Mr. 
Kaypro who clarifies the different ver- 
sions of his magic boxes. Ron Anderson 
continues on with 6809 assembler, but 
this time taking pseudo program steps 
and converting them into assembly code. 

With that 1 want to wish everyone a 
happy and prosperous holiday season. 
BiU Kibler. 

Gary A. Kildall 

The Computer Journal / #70 


Letters to the Editor 

All Readers 

MINI Articles 

/ have received many letters from Emmanuel 
Roche, but this last one certainly shows how 
much he considers Gary Kildall as one of 
our industries most important persons. 
Emmanuel 's researching of CP/M history 
and some of it 's internal secrets has cer- 
tainly enlighten many of TCJ's readers. I 
received these hand typed manuscripts after 
69 went to press. 

Now I still think that David McGlone 's (Z- 
Letter §32) review of Gary 's life and achieve- 
ments is a must read by everyone, but 
Emmanuel would like us to remember Gary 
by his work. In order for you to better un- 
derstand that work, he has given to me all 
the articles and discussions by Gary about 
CP/M. Thus we can get to better understand 
our loss by looking at Mr. Kildall's achieve- 

Unfortunately many of the articles and writ- 
ings are copyrighted and thus prevent me 
from running them in their entirety. I am 
allowed however to "review " them and quote 
sections in order to give you their flavor as 
it were. I need to comment that these ar- 
ticles amount to over 80K worth of text (30 
pages+), that has been retyped for you and 

What follows then, is a review of Gary 
Kildall's work, in order that we may better 
understand our loss. (I have put ***** to 
indicate that I skipped over some text.) Bill 

The History of CP/M (The following items 
were retyped by Emmanuel ROCHE.) 

"First word on a floppy-disc operating sys- 
tem " Command language and facilities simi- 
lar toDECSYSTEM-10 by Jim C. WARREN, 
Jr., Editor, DDJ, April 1976, p.5 

We have the first tidbits of information on 
the floppy-disc operating system to which 
we have alluded in past issues: 

The system, called "CP/M", runs on an 8080. 
It is available from Digital Research, P.O. 

Box 579, PACIFIC GROVE, CA 93950; 
(408) 373-3403. Its user interface is pat- 
terned after that of the DECSYSTEM-10. 
The file command include RENAME, TYPE, 
load/execute facility (type the name of an 
object file; it will be loaded and begin ex- 
ecution). File-names follow the DEC stan- 
dard of a 1-8 character name with a 1-3 
character suffix. An editor is included that 
has somewhat the flavor of TECO. There is 
a PIP facility that allows easy transfer of 
files to and from any available device, e.g., 
terminal, paper-tape I/O, cassettes, floppy 
discs on any drive, etc... Note; PIP is DECeze 
for Peripheral Interchange Program. Other 
systems software is likely to be included. 

This system already exists and has been in 
use for over a year. It was originally de- 
signed and implemented by Dr. Gary 
KILDALL, a Computer Science Professor at 
the Naval Postgraduate School in Monterey, 
and a well-known, independent consultant 
in the area of microprocessor systems soft- 
ware. Gary is also the designer and 
implementor of PL/M, the "industry stan- 
dard" high-level language for microproces- 
sors. PL/M was produced for Intel for their 

From our experience, this is the hottest deal 
going! It's cheap, as far as floppy-disc sys- 
tems for micros go. The software is well- 
designed; based on a well-known and easy- 
to-use operating system that has been around 
for a DECade. Additionally — major points 
worth considering — it has been in use for 
some time, it has been used by a number of 
people, and it is fairly completely debugged. 
We know Gary personally, know "where his 
head's at", and know that he backs his prod- 
ucts and is responsive to his customers. In- 
cidentally, he has an excellent and ongoing 
working relationship with Digital Research. 

"The time for floppy's is just about now!' 
by the Editor, DDJ, Aug.76, p.5. 

Things — most notably, prices — are com- 
ing down, fast, in the world of rotating mass 
storage appropriate for home computers. 
Prior to this, floppy disk subsystems have 
either been unavailable for hobby machines, 
or they have been priced for the industrial 
consumer (e.g., around $3,000 for a dual- 
drive system). Things have changed: A hob- 
byist can now reasonably expect to obtain a 
complete, assembled, single-drive subsystem 
for a price in the neighborhood of $1K. 

The best system we know of — and the least 
expensive — is available from Digital Sys- 
tems (ask for Dr. John TORODE). This is 
the same crowd that built Gary KILDALL 's 
original floppy interface over two years ago 
(see "First Word on a Floppy-Disk Operat- 
ing System" in the April 1976 issue of the 
Journal). Gary has yet to have problems 
with the system. Digital Systems also is 
marketing a low-cost, floppy-based devel- 
opment system to the industrial market. They 
know what they are doing. What is much 
more important is that Dr. KILDALL's fancy, 
DECsystem-10-like operating system — 
called CP/M — will run on DS's hardware. 
CP/M has been in use for OVER TWO 
YEARS in a production and instructional 
environment. It is well debugged, well docu- 
mented, and has some significant software 
subsystems available with it. 

"Disks and CPM". "Disks and the Floppy - 
A brief overview of how they work" by Rich- 
ard BATEMAN, in "INMC80", Issue:5, Oct- 
Dec 1981, p.37 

We are all familiar with the cassette re- 
corder attached to our NASCOM, it pro- 
vides us with low cost mass storage, and 
permanent storage for programs and data. 
The method of recording is governed by the 
type of signals the cassette can record. ***** 

CP/M and the Floppy. Much has been writ- 
ten about CP/M in this newsletter of late, 
but no-one has explained what it is. CP/M 
stands for Control Program for Microcom- 
puters. It was originally written to take the 

The Computer Journal / #70 

chore of handling DOS away, and make the 
disk system as transparent as possible. This 
end is achieved quite well, although CP/M 
isn't the friendliest piece of software around. 
Anyway, CP/M is an operating system much 
as NAS-SYS is, but revolves around disks, 
particularly floppy ones. CP/M is divided 
into 3 parts, CHIOS, CCP and FDOS. The 
CBIOS does all the I/O and is written for 
each system, as disk I/O and keyboards dif- 
fer. Now NAS-SYS and CBIOS are much 
the same, and indeed could be the same if 
the entry points were looked at closely. 

CP/M reads the Floppy. CP/M reads the 
disk by using a directory, that relates the 
logical name (thats what you call the file) 
and its physical position on the disk. CP/M 
does not use sector and tracks as in D-DOS 
but uses block numbers, each block may be, 
say, 8 sectors, and may therefore be 1024 
bytes. The directory entry has 16 bytes set 
aside to keep the block numbers for that file. 
If the block size is IK, then each file can 
have up to 16K bytes per directory entry, 
this is known as an extent. Files longer than 
16K require two or more consecutive direc- 
tory entries, the first telling CP/M that it 
extends to the next extent, etc. 

"Upgraded CP/M floppy disk operating sys- 
tem now available" DDJ, Dec 76, p. 51 

CP/M is a disk operating system designed 
for diskette-based computer systems which 
use the Intel 8080 micro-processor. The CP/ 
M software package is now being offered to 
the small computer user community. 

The CP/M operating system is distributed 
for an Intel MDS micro-computer develop- 
ment system, but can be easily altered to 
operate with a wide variety of customized 
hardware environments. Basic requirements 

a) Intel 8080-based micro-computer main- 

b) At least 16K of read/write main memory 

c) One or two IBM-compatible disk drives 
and controller 

Given these facilities, the CP/M disk sys- 
tem is "patched" by the user to communi- 
cate with the specialized hardware. The exact 
steps to follow in programming and patch- 
ing the CP/M system are given in the manual 
"CP/M System Alteration Guide". In fact, 
several popular mainframe and controller 
manufacturers currently support their own 
CP/M patch. 

"The Evolution of an Industry: One Person 's 
Viewpoint " (Cf. "Dr. DOBB's Journal", No. 
41. JAN 1980, Vols, Issue 1. p. 6), by Gary 
A. KILDALL. Digital Research. P.O. Bo.x 
579. PACIFIC GRO\^ CA 93950 


I was sitting quietly at my desk when 
Masatoshi Shima hurried into my office at 
Intel and asked me to follow him to his 
laboratory down the hall. In the middle of 
his work bench, among the typical snaggle 
of jumpers, oscilloscopes and multi-meters, 
sat a binocular microscope with spider-leg 
probes, all of which were subjecting a minute 
piece of silicon to helpless investigation. I 
peered through the microscope at the en- 
larged regular patterns with particular inter- 
est. As a consultant, my job was to design 
and develop certain software tools for Intel. 
One was INTERP/80, a program which simu- 
lated Intel's newly evolved 8080 micro-pro- 
cessor to be used by Intel customers on time- 
sharing systems. As I searched for some- 
thing recognizable, I hoped my simulation 
resembled the operation of Shima' s first 8080 
chip which had finally come to life. 

My proposal to Intel had been simple: I 
would provide them with a language, called 
PL/M, to replace serious systems program- 
ming in assembly language. The compiler 
would first be written in FORTRAN for 
operation on time-sharing computers and 
"cross-compiled" to the eight-bit processors. 
Next, we would write a PL/M compiler in 
PL/M and "boot-strap" from the time-shar- 
ing computer to a resident compiler operat- 
ing on Intel's new Intellec-8 development 
system. The first part was complete. PL/M 
cross compilers and INTERP simulators were 
implemented for the now-best-forgotten 
8008, as well as the 8080. Programs had 
been written and tested by Intel's software 
group, consisting of myself and two other 
people, and we were ready for the real ma- 
chine. Things were going well: the resident 
compiler would be the next step. 

Meanwhile, John TORODE redesigned and 
refined our original controller and produced 
his first complete computer system, mar- 
keted under his company name, Digital Sys- 
tems (which later became Digital 
Microsystems). The first commercial licens- 
ing of CP/M took place in 1975 with con- 
tracts between Digital Systems and Omron 
of America for use in their intelligent termi- 
nal, and with Lawrence Livermore Labora- 
tories where CP/M was used to monitor 
programs in the Octopus network. Little was 
paid to CP/M for about a year. In my spare 

time, I worked to improve overall facilities, 
and added an editor, assembler, and debugger 
which were predecessors of the current ED, 
ASM, and DDT programs. By this time, CP/ 
M had been adapted for four different con- 

In 1976, Glenn EWING approached me with 
a problem: IMSAI, Incorporated, for whom 
Glenn consulted, had shipped a large num- 
ber of disk sub-systems with a promise that 
an operating system would follow. I was 
somewhat reluctant to adapt CP/M to yet 
another controller, and thus the notion of a 
separated Basic VO System (BIOS) evolved. 
In principle, the hardware dependent por- 
tions of CP/M were concentrated in the 
BIOS, thus allowing Glenn, or anyone else, 
to adapt CP/M to the IMSAI equipment. 
IMSAI was subsequently licensed to distrib- 
ute CP/M version 1.3 which eventually 
evolved into an operating system called 

By coincidence, Jim WARREN and I were 
both consulting at Signetics Corporation 
during this time. Jim was then the editor of 
DDJ, and pushed for sale of CP/M to the 
general public. There was, at the time, a 
pervading paranoia among software vendors 
who feh that any and all loose software 
would be immediately "ripped-off by this 
immoral group of computer junkies. Jim's 
faith in the industry, however, led me to 
introduce the CP/M 1.3 system for sale on 
the open market at $70 per copy. In the 
months that followed, the nature of the com- 
puter hobbyist became apparent. In most 
case he was, like myself, in the computer 
industry and merely wanted a personal com- 
puter for his own endeavors. CP/M gradu- 
ally gained popularity through a "grassroots" 
effect and, to the amazement of the skeptics, 
the rip-off factor was practically nil. A new 
company called Digital Research was formed 
to support CP/M, develop new products, 
and provide administrative functions. 

"CP/M: A Family of 8 and 16-Bit Operating 
Systems" (Cf BYTE, JUNE 1981, p.216), by 
Dr Gary KILDALL, Digital Research, P.O. 

This article is about microprocessors and 
CP/M: where they came from, what they 
are, and what they're going to be. Where 
they came from is history, what they are 
today is fact, and what they will become is, 
like any projection of technology, pure "sci- 
ence fiction" speculation. CP/M is an oper- 
ating system developed for microcomputers. 

The Computer Journal / #70 

But as microprocessors changed, CP/M and 
its related programming tools evolved into a 
family of portable operating systems, lan- 
guages, and applications packages. 

The value of computer resources has changed 
dramatically with the introduction of micro- 
processors. Three major events have pre- 
cipitated a revolution in computing: hand- 
threaded core memory has been replaced by 
•mass-produced semiconductor memory, mi- 
croprocessors have become plentiful; and 
IBM decided that the punched card is obso- 
lete. Low-cost memory and processors have 
reduced the cost of computer systems to a 
few hundred dollars, but IBM's specifica- 
tion of the floppy disk standard has made 
the small computer system useful. 

In the early days of the 8080 microproces- 
sor, a small company called Shugart Associ- 
ates was taking shape up the street from 
Intel. Shugart Associates, along with a num- 
ber of other companies, viewed the floppy 
disk as more than a punched card replace- 
ment: at that time the primary low-cost stor- 
age medium was paper tape (used in appli- 
cations ranging from program development 
to word processing). At a cost of $5, a 
floppy disk held as much data as two hun- 
dred feet of paper tape, and a disk drive 
retailed for only $500 — an unbeatable com- 
bination. Memory, processor, and floppy- 
disk technology improved, and by the mid- 
1970' s, a floppy-based computer could be 
purchased for about one quarter of a 
programmer's annual salary. Quite simply, 
it was no longer to share computer resources. 

The emergence of software as a problem- 
solving tool 

Microprocessors are a natural consequence 
of our technology. I recently visited the Brit- 
ish Science Museum, where two particu- 
larly interesting historical developments 
were on display. The first exhibit chronicled 
the development of the finely matched iron 
and brass steam engines, complete with 
magnificent gauges, gears, whistles, and 
valves, that founded the Industrial Revolu- 

I followed the sequence of displays, from 
BABBAGE's difference and analytic engines 
to great brass calculators and early punch 
cards, past relay and vacuum tube proces- 
sors to unit record equipment, then to tran- 
sistor and random-logic computers and semi- 
conductors and, finally, to a single Intel 8080 

Application languages 

Application languages form the top level of 
support for application programming. How 
does this level of language differ from other 
language levels? First and foremost, an ap- 
plication language contains the operations 
and data types suitable for expressing pro- 
grams in a particular problem environment. 
FORTRAN (FORmula TRANslation), for 
example, was designed in the late 1950s for 
scientific applications; FORTRAN programs, 
therefore, consist primarily of algebraic ex- 
pressions operating upon binary floating- 
point numbers expressed in scientific nota- 

The evolution of PL/I (Programming Lan- 
guage One) provides a good example of re- 
finement in application languages. PL/I is 
not a new invention: rather, it was defined 
by a committee of IBM users in 1960 as a 
combination of ALGOL (ALGOrithmic Lan- 
guage), FORTRAN, and COBOL, with a 
liberal sprinkling of new facilities. ALGOL'S 
principal contribution was block structure 
and nested constructs, while FORTRAN con- 
tributed scientific processing and COBOL 
added commercial facilities. This combina- 
tion produced a large, unwieldy language 
with twists and nuances that can trap the 
unwary programmer. Nevertheless, PL/I was 
quite comprehensive, and it served as the 
basis for uncounted numbers of application 
programs on large systems. One noted use of 
PL/I was in the implementation of the 
Multics operating system at MIT unu^. 
Project MAC. 

System languages 

A system language is a high-level machine- 
oriented programming language used to 
implement so-called "system software", in- 
cluding operating systems, text editors, 
debuggers, interpreters, and compilers. In 
the early days of computing, virtually all 
system software was implemented in as- 
sembly language. One revolutionary ma- 
chine, the Burroughs B5500, used a variant 
of ALGOL-60 as its only system-program- 
ming tool and appeared in the early 1960s. 
The machine was a commercial success 
against the other major mainframes, proving 
that assemblers were no longer necessary. 
Many successful system languages followed 
Burroughs' ALGOL, including the C lan- 
guage, produced at Bell Laboratories in the 
late 1960s, which served as the basis for the 
UNIX operating system. 

PL/M: the base for CP/M 

In 1972, MAA (Microcomputer Applications 
Associates), the predecessor of Digital Re- 
search, consulted with the small, aspiring 
microprocessor division of a semiconductor 
memory company called Intel Corporation. 
MAA defined and implemented a new sys- 
tems-programming language, called PL/M 
(Programming Language for Microcomput- 
ers), to replace assembly-language program- 
ming for Intel's 8-bit microprocessor. PL'M 
is a refinement of the XPL compiler-writing 
language which is, in turn, a language with 
elements from Burroughs Corporation's 
ALGOL and the full set of PL/I. 

Operating systems 

Operating systems, too, have become more 
refined. But why do we have operating sys- 
tems at all? In the 1960s we used expensive 
mainframes with power-hungry central pro- 
cessors and magnetic-core memory. Down- 
time for complicated card readers, printers, 
and backup data-storage devices was high, 
requiring constant maintenance. A card-ori- 
ented "batch" operating system provided two 

The CP/Tvl family 

CP/M was, however, completed by MAA in 
1974. It included a single-user file system 
designed to eliminate data loss in all but the 
most unlikely situations, and used recover- 
able directory information to determine stor- 
age allocation rather than a traditional linked- 
list organization. The simplicity and reli- 
ability of the file system was an important 
key to the success of CP/M: file access to 
relatively slow floppy disks was immediate, 
and disks could be changed without losing 
files or mixing data records. And because 
CP/M is a Spartan system, today's increased 
storage-media transfer rates simply improve 
overall response. The refinements found in 
CP/M are based on its simplicity, reliabil- 
ity, and a proper match with limited-resource 


As single-user CP/M became widely ac- 
cepted, Digital Research began to develop a 
new operating system for real-time process- 
ing. The design called for a real-time nucleus 
to support cooperating sequential processes, 
including a CP/M-compatible file manager 
with terminal-handling capabilities. This 
operating system, called MP/M (Multi-Pro- 
gramming monitor for Microcomputers), is 
a further refinement of the process model 

The Computer Journal / #70 

found in Intel's RMX and National's 
Starplex. As a side effect, the combination 
of MP/M's real-time nucleus with the ter- 
minal handler and the CP/M file system 
produces a traditional timesharing system 
with multiprogramming and multiterminal 


CP/NET, introduced in late 1980, leads a 
series of network-oriented operating systems 
that distribute operating system functions 
throughout a network of non-homogeneous 
processors. CP/NET connects CP/M request- 
ers to MP/M servers through the use of an 
arbitrary network protocol. Similar to CP/M 
and MP/M, CP/NET consists of the invari- 
ant portion, along with a set of field- 
reconfigurable subroutines that define the 
interface to a particular network. For pur- 
poses of CP/NET, this interface needs only 
provide point-to-point data-packet transmis- 
sion. Since the actual data transmission 
media are unimportant to CP/NET, any one 
of the number of standard protocols can be 
used, from low-speed RS-232-C through 
high-speed Ethernet. Physical connections 
are also arbitrary, allowing active hub-star, 
ring, and common-bus architectures. 

PL/I: the application language 

In 1978, Digital Research investigated the 
final level of software support: application 
languages. One such language was to be 
supported throughout the operating system 
product line, and the choice would have to 
be a multipurpose language. Further the lan- 
guage would have to be an international 
standard to promote the generation of soft- 
ware by independent vendors. Standard Pas- 
cal seemed a logical choice but was rejected 
for several reasons. First, Pascal is an AL- 
GOL derivative with scientific orientation. 
Commercial facilities in the standard lan- 
guage are absent: decimal arithmetic, file 
processing, string operations, and error-ex- 
ception handling were essenfial. Further, 
separate compilation and initialization of 
tables were not in the language. There was 
a temptation to extend Pascal in order to 
include these features, but these extensions 
would have defeated the benefits of stan- 

New processor architectures 

We've spent little time discussing processor 
refinements. What is happening to our soft- 
ware tools as we augment our 8-bit ma- 

chines with the more powerful 16-bit pro- 
cessors? Will 16-bit processors replace 8-bit 
machines, or are they simply a temporary 
phenomenon in the transition to 32-bit ma- 

There are several considerations when an- 
swering these questions. First, 8-bit machines 
are economical to produce, their software 
systems are mature, and they satisfy the 
needs of a substantial computer base. There- 
fore, we can safely assume that 8-bit ma- 
chines are here to stay. Newer 16-bit ma- 
chines are marginally faster, but they have 
substantially more address space. To use 
this additional address space, the computer 
must contain more memory, which increases 
the computer system cost. 

As system costs increase, the margin be- 
tween low-end minicomputers and high-end 
microcomputers diminishes, placing micro- 
computer hardware and software manufac- 
turers such as ourselves in direct competi- 
tion with major minicomputer manufactur- 
ers. The 16-bit machines, by their nature, 
introduce memory segmentation problems 
that are not present in 32-bit processors. 

Finally, we should note that 16-bit mini- 
computers are already out-moded, and all 
serious manufacturers are pushing 32-bit 
machines. This leads to the following con- 
clusion: if we are tracking the minicomputer 
worid, we can assume that the future will be 
with the 32-bit processors. 

Software vendors 

We've concerned ourselves with three lev- 
els of software tools that support the most 
important level: the application programs. A 
major reason for CP/M's popularity is the 
general availability of good application soft- 
ware. At last count, there were about 500 
commercially available CP/M-compatible 
sofhvare products. 

"PUI For Limited Resource Computers" by 
Gary A. KILDALL (Microsystems, Jan/Feb 
1982, pp. 28- 2 9) 

PL/I, Programming Language One, has in 
one form or another been with us for nearly 
twenty years. Although a pragmatic language, 
it was considered large, unwieldy, and dif- 
ficult to implement. Recently, however, the 
language has been revitalized through the 
efforts of the American National Standards 
Insitute (ANSI) Technical Committee X3J1 
where the General Purpose Subset language 
was defined. This so-called "Subset-G" lan- 

guage is upward compatible with full PL/I, 
but is designed expressly for mini-computer 
implementation. The elements selected for 
inclusion within Subset-G are the most com- 
monly used facilities used in commercial, 
scientific, and educational application pro- 
gramming. Redundant language constructs, 
little-used facilities, and error-prone state- 
ment forms were eliminated, resulting in a 
sub-language which most observers believe 
is superior to the full language in many 

PL/I was originally conceived in the early 
1960's by the Advanced Language Develop- 
ment Committee of the SHARE Fortran 
Project, in the wake of interest created by 
ALGOL, FORTRAN, and COBOL. Elements 
of each of these languages were incorpo- 
rated into the original design: block struc- 
ture, nested scope of variables, procedure 
formats, and array referencing were, like 
PASCAL, derived from ALGOL. Scientific 
facilities came from FORTRAN, including 
separate compilation, expression formula- 
tion, floating-point arithmetic, some I/O for- 
mation, and a wide variety of transcendental 
functions. Commercial processing in PL/I 
was derived from COBOL, including struc- 
tures, decimal arithmetic, file processing, 
and picture formats. A variety of new state- 
ment forms were added to allow character 
string processing and error-exception han- 
dling, which where considered essential for 
high-level application programming. Real- 
time multi-tasking facilities were also added 
to allow PL/I to be used for systems pro- 
gramming as well. The language which re- 
sulted from this design effort contains more 
built-in data types, arithmetic operations, 
and general-purpose programming facilities 
than any other programming language avail- 
able today. But herein lies the primary dif- 
ficulty with full PL/I. The language is too 
large to implement effectively on any but 
the largest mainframes. The complexity of 
the language also inhibited proper use of all 
language features, while the unwary pro- 
grammer was often trapped by strange twists 
and nuances of the language. Nevertheless, 
PL/I has proved to be a practical, pragmatic 
language for application programmers over 
the past several years, through implementa- 
tions on a variety of mainframe computers. 

The Digital Research PLA-80 programming 
system project was started in 1978, and com- 
pleted two years later. PL/I-80 is based upon 
Subset-G, with nearly all of the Subset-G 
features, and operates under the Digital 
Research CP/M, multiprogramming MP/M, 
and CP/NET network operating systems for 

The Computer Journal / #70 

8080, 8085, and Z-80 microprocessors. The 
PL/I-80 programming system itself consists 
of the compiler, macro assembler, linkage 
editor, program librarian, and run-time sub- 
routine library. 

The PL/I-80 programming system is cur- 
rently being transported to 16-bit proces- 
sors, with initial support for the Intel 8088 
and 8086 processors, so that designers may 
select either 8-bit or 16-bit processors for 
their applications programs. The transition 
to the Intel processors is simplified in two 
ways. First, the compiler itself is written in 
PL/M, Intel's high-level system language, 
with portions of the run-time system written 
in PL/I. Thus, only the semantic handlers 
need to be altered, along with conversion of 
the space and time critical run-time subrou- 
tines, such as the floating-point library, which 
are implemented in assembly language. 

/ hope you have gotten the flavor and will 
pursue the references for the entire text. Dr. 
Dobbs' entire publishing history is avail- 
able on CDROM from them. The other ref- 
erences should be available in technical li- 
braries and from friends. BDK. 




Roger Hanscom has been connecting 1 .2MB, 
5" floppy drives to older systems which ex- 
pect 8" drives with no modification. This is 
an interesting idea which could greatly en- 
hance the life of these older machines, since 
all of the 8" drives are wearing out. I sug- 
gested he write to you about writing an 
article about it. 

Another thing he's been doing is saving all 
his EPROMS on floppies. We easily forget 
that the insulated-gate EPROMs are only 
guaranteed to keep data for about 7 years - 
and our older machines could be well be- 
yond that. Imagine trying to find a replace- 
ment EPROM for an old S-100 board or a 
Kaypro or Xerox 820. Scary thought! In fact 
maybe we should collect a library of the 
ROM images. 

Forwarded message: 

From: roger hanscom 

Subject: Re: disk upgrades, etc. 

Hi Rick — 

There was, on some, a ROM monitor which 

could be enabled instead of the TurboIX)S 
load routine. There are several models of 
these boards, too... 

- IMS 740 - Z80 + 64K 

- IMS 1000 - 80186 + 128K 

- IMS XXX - Z80 B or H + 128K 

Most of mine are Z80 with 64k memory. 
The EPROMS on them have a very simple 
little program that appears to be able to 
download and store in memory. They have 
CTC, PIO, SIO/0, and, of course, the 8255 
that is the bus interface. I'd love to find out 
what the port numbers are for all the periph- 
erals. Also I discovered that there is a jumper 
on the board that allows it to run. This must 
be under software control, but I've yet to 
discover how to turn it on, other than install- 
ing that jumper. 

As it happened I forgot to get the drive. I did 
get a Kaypro 10 for $20 - it works fine! - and 
a digitizing pad for $10, and a few other 
bargains... but I just got too sick from rag- 
weed pollen to see the whole fest. 

That's a pretty good price! 

In the meantime 'both* of the Qume DT8's 
in my IMS system are flaking out. The sys- 
tem has had more or less continuous use for 
15 years, so I can't complain. I have two 
Shugart 851 's, condition unknown, and two 
Tandon half-heights, but it turns out that 
one is single-sided. Also have a couple more 
Qumes in the storage room, one known dead. 

Sounds like you really need to get some 
1.2Mb 5.25"s 

But then I suppose - WAIT - we need a drive 
which actually changes SPEED, not one of 
the ones that fakes it by letting you use a 
different data rate. Does the Mitsumi do 

There is a jumper to set spindle speed to 300 
or 360. There is one configuration that is 
"300/360 switchable", but I can't see what 
would "switch" it. 

1 sent mail to Bill K's CompuServe account, 
so we'll see if he gets it. I've had no luck 
with getting e-mail to 

I'm working on getting you a copy of those 
manuals. Perhaps I can Xerox reduce them. 


OK Roger and Rick, seems this discussion 
on using drives needs to be settled a bit 
more. I had understood that 3.5" drives in 

their high density version (1.4 MB) were 
identical to 8 inch drives in speed and tracks. 
You two make me think I am wrong here, 
and it is AT 5 inch drives. I guess what is 
really called for is some comparisons and a 
little bit of research about all the drives, or 
did I Just layout another article to be done. 

I believe I did ask Roger by return e-mail to 
try and do me an article, but I am not sure 
he has the resources we need to really fill in 
all the gaps. Now when I worked at Teletek, 
they sold a simple 8 to 5 adapter that shifted 
the control lines around. I made a few later 
for myself and it really is rather simple. So, 
adapting the cabling from 8 inch interfaces 
to 5 or 3 inch is rather simple. The problem 
is not lines, but speeds, steps, and tracking. 

Well thanks for the spin on using 5 inch 
drives instead ofS's. I will be looking to do 
more or see more later. Thanks. Bill 


Dear Mr. Kibler: 

It's been a while since I last wrote to _TCJ_, 
but it seems I don't write unless something 
provokes me in some manner. 

I'm glad to see you haven't lost your enthu- 
siasm for an ISA-bus Z180 system. I'd very 
much like to see something like this myself 
My main question is how you see such a 
board being implemented. One possible 
design would be a stand-alone SBC that 
uses an ordinary AT-class 'BM clone as the 
I/O processor (handling the physical devices 
such as the keyboard, screen, and disk 
drives). Another design would have the Z180 
card be the bus master on an ISA passive 
backplane (such as Brad Rodriguez's 6809 
multiprocessor cards). What type of imple- 
mentation did you have in mind? 

In my first letter, I mentioned that my goals 
for my Amiga 500 were TeX and CAD work. 
The CAD work is still too expensive for a 
poor college student to afford, but TeX is up 
and running beautifully thanks to Georg 
Hessmann's PasTeX implementation. 
Thanks to an Amiga implementation of 
MetaFont, 1 can generate fonts and get beau- 
tiful hard-copy output on my dot-matrix 

My Amiga 500 has grown quite nicely in the 
year or so since my first letter. It sports some 
respectable hard disk space and even a CD- 
ROM drive. Actually, the CD-ROM drive is 
a Commodore CDTV that is networked to 

The Computer Journal / #70 

the A500 \ia their parallel jxjrts and ParNet 
device driver software. As scxm as the CP/M 
CD-ROM starts shipping. I'll be ready for 
it! (By the way, "CDTV" stands for "Com- 
mcxiore Dynamic Total Vision" and is one 
killer audio CD player in addition to being 
a complete Amiga 500 with CD-ROM drive 
itself!) Best part is, it was ail cheap to get 
and simple to put together. 

In some brief correspondence that followed 
my first letter, you addressed the question of 
"user support" for the F.pson QX-10. If you 
were asking about organized user groups, 
then I must say that I know of none right 
now — although I've heard of a few in the 
past. Even then, I don't have any informa- 
tion about them. QX-IO users seem to be 
pretty rare in the U.S., but it seems there's 
a bit stronger following in Europe. 

A plea for help came to me from Emmanuel 
Roche in France, fonvarded to me in e-mail 
by Tilmann Reh. Seems Mr. Roche has a 
number of Epson QX-lO's to which he'd 
like to adapt Mr. Reh's 8-bit IDE host 
adapter. At the time I didn't have the skill or 
confidence to attempt such a project as that, 
so I forwarded his request to Wayne Sung. 
Wayne accepted the challenge. 

After a few months of working on an appro- 
priate decoder off and on, Wayne had come 
up with a prototype. It turned out that the 
IDE drive he had was faulty, so I sent him 
one I'd scavenged from a dead GRiD 
System's '286 luggable. With it, Wayne 
verified that his control sequencer EPROM 
was working property. When Wayne returned 
the drive to me, he included two of the 
decoder EPROMs and a preliminary sche- 

I set about collecting the parts to build my 
own version of the IDE host adapter - in 
this case, for my own QX-10, since it would 
require the least additional work. (The de- 
coder EPROM is effectively system inde- 
pendent.) I uncovered a couple of errors in 
the schematic and some errors in the assem- 
bly source for the QX-10 BIOS patches. 
Once those were fixed, I had two 8MB hard 
disk partitions running on my 20MB Conner 
CP3022 IDE drive! 

I should point out that this was my first 
construction project ever I've since used 
the other EPROM to build a fairly generic 
IDE host adapter, but I'll need to build some 
other hardware to interface it to a system. I 
have a Davidge DSB 4/6 SBC that would be 
ideal as a test platform, but I've got more to 
do on it before I can think about writing a 
hard disk BIOS for it. (Namely, I need to 

finish disassembling and commenting the 
existing BIOS — I don't have source code for 
the actual CBIOS, just a skeleton BIOS.) 

One thing I learned is that the support strat- 
egy for European QX-10 users differs quite 
a bit from that for North American (US.?) 
QX-10 users. The biggest example is that 
European users use a different BIOS imple- 
mentation (MF-CP/M), get BIOS source code 
with the package, and even have CP/M Plus 
for the QX-10. Hard disk systems are up to 
the user to implement, but at least they have 
the BIOS source to work with. 

North American QX-10 users get a canned 
banked CP/M 2.2 implementation with (lim- 
ited) built-in hard disk support and that's it. 
No BIOS source, no CP/M Plus. (The last 1 
heard, BIOS source is still available, but 
Epson still wants $500.00 per copy.) 

While working with the BIOS patches to 
enable IDE support, I took steps to improve 
upon my existing Comrex Comfiler hard 
disk (the standard hard disk system for North 
American QX-10 systems). My Comfiler has 
a 6-head IMI-5018 hard disk in it (as a result 
of playing "musical parts" with another 
machine). The stock QX-10 BIOS only un- 
derstands 4 heads. After a bit of study, I 
implemented a 16-bit "divide-by-n" routine 
to replace the original BIOS code that trans- 
lates the CP/M logical track to cylinder and 
head for the hard disk and set it up to divide 
by 6. 

I then turned a QX-IO 4-head hard disk 
format program into a 6-head format pro- 
gram. Soon, I had a 1 4.2MB Comfiler in- 
stead of a 9.5MB Comfiler. I'll never fill 
that up! I also included some assembly- time 
switches for IDE hard disk support. 

I started work on some generic IDE/WD 1 OOx 
utilities, starting with a C version of Tilmann 
Reh's IDE ID program, written with Aztec 
C-n vl.06d. I've hit a serious snag with this 
in that I'm having trouble with unsigned 
long integers (which I need for holding the 
total number of sectors on the drive). When 
trying to print the disk's size in megabytes, 
I get nonsense. Needless to say, develop- 
ment is on hold until I can either figure out 
Aztec C's hangups or switch to Hi-Tech C 
or perhaps Turbo Modula-2 (which are what 
I have most readily available). 

In the week before I had to come back up to 
school, I learned quite a bit about the SASE 
SCSI interface and how to design a host 
adapter and write a device driver for it. I 
also managed to find that my Davidge DSB 
4/6's expansion connector is tailor-made for 

attaching a SASI host adapter with DMA I 

capabilities. All interesting stutT and i 
wish I could spend more time on it. 

1 probably failed to be specific about any- 
thing again. This letter seems to have turned 
into a "How I Spent My Summer Vacation " 
report, and probably an incoherent one at 
that. One of these days I'm going to sit down 
and write at length and in detail about a 
single topic, but either the time or the provo- 
cation is lacking. In the meantime, there are 
so many nitty little things to learn about, 
and I can only learn about them by taking 
things apart and playing with them. 

Take care and enjoy. 

John D. Baker ->A TransWarp'802'd Apple 
//e CardZlSO Z-Systcm nut,'/ 
BBSs; JOHN BAKER on PIC of the Mid- 
Town [(713) 961-5817] 1:106/31, 
The Vector Board [(716) 544-1863], Z-Nodc 
#45 [(713) 937-8886] 

77ja/ is great John, your advice and discus- 
sion I am sure has helped many of our 
readers. I have yet to gel any "how it went ' 
articles on the IDE drive project. Yours is 
the first I have heard about. Maybe others 
now will be willing to fill us all in on their 

How about more on the QX-10 work, and 
getting Wayne to start writing again for 
TCJ. Wayne did some networking articles in 
times past, and it is nice to see he has time 
to still tinker. It is most interesting to see the 
different way companies handle the same 
item in Europe, compared to the States. Thai 
of course is one reason I hunted down Helmut 
for the European Beat series. I think Atari 
still sells 90% of their machines to Europe. 
and leaving the US retailers out to dry (or 
die as is more correct). 

On the ISA Z80 system, I am thinking now 
the new 40MHZ Z380 might be the way to 
go. It runs both regular Z80 code as well as 
advanced commands to do 32 bit opera- 
tions. It has four sets of registers which 
means you could do a 4 users CP/M system 
very simply. As to being a master or slave, 
I figured a master is best. No need to build 
a slave, just use MYZ80. But for a real Z80 
system using the cheaper ISA bus I/O de- 
vices was my idea. I might also point out 
that many companies are now using 68000 
based ISA bus systems for real time control, 
usually running OS9 68K. From what I have 
heard, those users are very happy with the 

The Computer Journal / #70 

results. So why not do the same, but with a 
Z80 or Z380 system. Some might think of 
moving their STD BUS projects to it, espe- 
cially with the option of 40 MHZ perfor- 

So let me know what you think of the ISA/ 
Z80 idea. For you, I guess the main question 
many of the QX-10 users will have now, is 
how they can get CP/M Plus for their ma- 
chines, and oh yes, IDE decoders? Thanks 
John, great letter! Bill Kibler. 

Sub: CoCo serial I/O 
From: James Jones 

Concerning your question about CoCo serial 
I/O in TCJ 69: the stock CoCo indeed bangs 
the bits on half a PIA (the other half reads 
switch closings on the keyboard). Tandy 
made two cartridges for the cartridge slot or 
Multi-Pak Interface that would do serial I/O 
with real serial I/O hardware (a 6551 ACIA 

1. The "Modem-Pak," which had a 300 bps 
modem and the serial chip, and, I believe, 
some minimal comm program in ROM (a 
fellow named Marty Goodman, whom you 
should contact if you're interested in the 
CoCo, came out with instructions on how to 
disable the ROM and modem, so you could 
just use the ACIA as a real serial port). 

2. The "RS-232 Pak," which had an ACIA 
chip and a DB-25 connection. 

Third-party companies came out with other 
serial hardware, notably Disto/CRC and Ken- 
Ton. There are still third-party companies 
doing CoCo stuff; where serial hardware is 
concerned, you would want to contact Rick 
Uland with CoNect, or the Ken-Ton folks, 
who are still around and also make a good 
SCSI interface for the CoCo. (One third- 
party company, which as far as I know is no 
longer around, made a cartridge with *four* 
serial ports for the CoCo.) 

(BTW, probably the best compact source of 
CoCo information, this side of ordering the 
Technical Manual from Tandy, is Frank 
Swygert's book 'Tandy's Little Wonder*. A 
significant part of it is Alfredo Santos's his- 
tory of the CoCo, and Mr. Santos mentions 
OS-9 exactly twice, so IMHO that aspect of 
the history is not compkte, but still it's a 
book well worth havkig \i you're interested 
in the CoCo. My ifAe uaociation with Fama 
Systems is that I lubsciibc to *The World of 
68 Micros* and think it's a good magazine.) 

James Jones (fonner CoCo user, current MM' 
1(a) user) 

Opinions (and any errors) herein are those 
of the author, and not necessarily those of 
any organization. 

WellJames, nice to hear from you and to get 
those bits of knowledge. The CoCo is still in 
my opinion an underrated machine, except 
by those who still use it And Yes OS9 is very 
important to it and many others as well. 

I think most users feel "bit-banging" is a 
bad way to move data, but depending on the 
instruction set, the overhead is often little 
more than using regular serial devices. 
Motorola 's 6805 programmers manual has 
a very good example of bit-banging, if you 
want to see a simple implementation. 

What I guess we need is the actual address 
or phone numbers of the companies you 
listed so I can add them to the User Groups 
support list. MM/l(a)? How about a little 
info on that one, can 't match it up to any- 
thing I am aware of yet. Thanks . Bill. 

From: edu@ineto i » 
Sub: bound volumes 

hello and tnxs for putting out a great 'zine' 

i read it THRU every issue and am 

seriouly considering gettiing a full set of 
back issues BUT it is rather $$ (at least for 
me and my miserly ways) .... in any event i 
noticed u had indicated issue 32 was TEM- 
PORARILY out of stock but now with issue 
69 is back in stock with 15 issues, this 

brings up a question in eariier issues u 

had mentioned u would be binding these up 
and creating volumes .... to wit; are u still 
considering this? if so when (and if so), and 
with what issue do u intend to stop doing so? 

etc since the bound volumes make sense, 

and are a bit less $$ ... i may well consider 

this if and when u are complete ... etc in 

any event PLEASE keep up the gud work 
and best regards ... baab 

Well I guess some answers from me are 
needed here. I made 15 copies of issue #32 
to hold readers till I can make masters for 
the next volume. Another reason is the other 
issues in that next group all have at least 15 
copies waiting to be sold. So I am sort-of 
waiting to get the numbers closer to all 
gone. As to the issues in Volume 5, 32 to 37, 
and maybe volume 6 will be needed about 
then as well (with 38 to 43). So there you 

have the facts from the source. Thanks for 
the inquiry. Bill. 

Dear Bill 

Please extend my subscription to The Com- 
puter Joumal for another 2 years. 

CP/M seems to be dying away. I am in the 
Windsor Bulletin Board, which has had a 
hardware failure and will not be coming 
back on stream. Other clubs do exist. I am in 
BOOG (British Osborne) but if I seek knowl- 
edge, all the members say "I have been on a 
PC for years, you are on your own". They 
had a so-called repair evening, some ma- 
chines in a sorry state came in, they were in 
an equally sorry state when they went home! 
All back We did have a rather downputting 
atmosphere in most clubs to what I could 
call the second generation of members. We 
were 2nd class. If one had an AMSTRAD, 
then horror of horrors, how down market. 
That is why the CP/M UG Died, the maga- 
zine was full of editorial comments that 
drove readers away. Towards the end, it 
became Yes such a thing can be done, in fact 
I have done it. So you can do it yourself (go 
away, implied). 

One thing you may wish to mention is that 
the CP/M disassembly programs advertised 
(and editorially mentioned) in the TCJ ARE 
STILL AVAILABLE for those who need 
them. I do not have the name with me. CP/ 
M 2.2 and CP/M plus. 

I have recently purchased Z system, NZ, 
DSD, ZMAC and others. Be warned, these 
will NOT LOAD on the OSBORNE Execu- 
tive. Jay Sage says he has never seen before 
the error messages that I sent to him. This 
may be on a par with HISOFT products sold 
over here (and the USA?). Their CP/M ver- 
sions will not load. The editor coming with 
5 programs vary a little. Each stops at a 
different part of the autosetup. 

Someone has said it is the Osborne inter- 
rupts, but Jay wrote it can't be that. Has 
ANYONE ever got the Z system etc to run 
I have all diagnostics discs, manuals etc and 
everything agrees with manufacturers spec. 
Osborne did publish the full details of bios 
etc, but not knowing what could be blocking 
the system, this does not help. (This is why 
I got DSD, I hoped to find out why the 
HiSofl stuff did not run). 

I have been writing to a lot of your old 
advertisers hoping to find one that still makes 
the realtime clock that plugs in with a Z80 
in piggyback socket. No replies. Do your 

The Computer Joumal / #70 

readers know of anyone? OR do they have 
one I can purchase. Even the circuit would 
help. I could make it, but do not know how 
to design it. Could you consider a center fold 
on such small circuits? They should (?) be 

I also wrote (my postage bill is high!) to 
SlOO Herb. As he told me the Osborne is 
Not SlOO, but I knew that. Could someone 
write & say why I could not add an extra 
socket wired to the SlOO standard & change 
any CP/M computer to be an SlOO device. I 
always thought from Sol Libbes articles that 
it was a hardware thing, and did not need 
special software? Am I being an idiot? Does 
the same apply to SCSI (with chip as a line 
driver if needed)? It is the simple things that 

Again, Osborne etc are SSDD. If I wish to 
change the hardware and bios (easy) to 
DSDD WHICH machine's format should I 
emulate for ease for exchange with others? 
(For SSDD, I have found getting stuff on 
Kaypro H is easiest and I then change it to 
Osborne 'with Media Master). Lacking a 
DSDD equivalent of Mediamaster (and NOT 
wanting to have to use SYDEX PC Pro- 
grams to alter CP/M discs more than I have 
to). Is there a semi-generic DSDD (and if so 
what are its details as far as CP/M needs to 

Finally, We are still in the boondocks over 
here. Email is not readily available in busi- 
ness or at home, so when only that is given 
as a contact "address" with your authors, it 
does block me, at least! It must apply to 
others, even in USA! 

Regards! Keep up the good work! John But- 
ler, London, England. 

Wow John, lots of stuff going on over your 
way. To start from the bottom and work up, 
I do try to get my writers to provide real 
addresses and contact info, but not every- 
one wants to cooperate. My feeling is, send 
it to me and I'll forward or reroute it to 

As to a disk format, I think your idea of 
using Kaypro format if you can change the 
BIOS is correct. As to a standard, the PC 
clone format is Just about the only real 
standard out there. And I believe Jay has a 
program for Zsystem that will read DOS 
disks, so you might think about that option. 
Actually the way I feel many should con- 
sider is adding a hard drive and just doing 
modem from other sources. Or, get an ac- 
tual Kaypro and have it talk to the Osborne 

serially, gives you an extra CP/M machine 
as well. 

On problems with other people wanting CP/ 
M to go away, what can I say? I think they 
are wrong for considering it dead. It really 
shows too, as you said when the broken 
system entered and then left stilt broken. I 
find most PC Clone users have very little 
idea what goes on inside their machine, and 
often could care less. What TCJ tries to 
teach by using the older and simpler ma- 
chines is how they work and why they work 
that way. 

As a teacher I have found many other teach- 
ers glossing over or ignoring valid ques- 
tions that might require study on their part. 
Since teachers are in the business to explain 
things and they often don 't when it comes to 
the insides of machines, how can we expect 
users, often supposed super users to be able 
to explain things as well. 

The final word I guess is that only TCJ is 
left to aid and provide support for non-pc 
systems. We have been doing it for over ten 
years and have to consideration to stop do- 
ing so. I do plan on continuing to expand 
coverage so PC using wanting to know about 
the insides can get a little help here, but 
have no fear it will always be Just a little 
help, with the main details found in smaller 
systems like Z80s or 6809s 

Thanks for writing and don 7 lose faith. Bill. 

Dear Bill, 

While going through my CPUZ180 develop- 
ment notes, it entered my mind that the part 
on a floppy disk problem might make a story 
for your magazine. I am submitting the re- 
sult for what it is worth. 

On another matter, the PT IDE802 IDE and 
Centronics interface, derived from the 
CPUZ180 SBC's CPUZIDE chip, uses the 
IDE engine from the PT IDE 100 SlOO con- 
troller. This chip can provide most 8-bit 
CPU based designs with IDE and Centronics 
capability at very little or no extra logic. The 
core is an EP1810 PLD, a close cousin of the 
EP1830 housed in the PT IDE 100, but not as 
power hungry. I enclose a preliminary spec 
sheet for your perusal. If you think your 
readers will be interested I can put some 
words together on it, or feel free to use the 
sheet itself The PT IDE802 is currently 
available from here in sample quantities for 
AU$55,00 "(about US$41.00). Please con- 
tact me if you require something more about 

Since my last letter to you re: the CPUZ180 
I made some changes to the memory select 
circuitry to improve access timing. The re- 
sult was that even slow 120 ns FLASH 
memory worked on zero waits. I will still be 
fitting the faster 70ns parts, but it is nice to 
know there is plenty of margin. Consequently 
the beta version boards are operating with- 
out wait states. I am getting some photos of 
a board and will send you one when they 
come to hand. 

Regards, Claude Palm, cnr. Moonah & Wills 
Sts., Boulia, QLD. 4829, Australia. (077) 

Thanks Claude for the extra information. I 
like your article and it will be in # 71 space 
permitting. The Z-Letter printed the picture 
of your CPUZ180 on their cover and your 
letter describing it's operation within. As 
you can see I printed the description and the 
two drawings of your IDE802. I hope the 
information is enough for our readers to see 
if it provides a better way for them to inter- 
face than using several TTLs. 

Since your project is for more than one unit, 
and allowed for several variations from one 
development project, it is easy to see that it 
is very cost effect in your case (also fits on 
a single board better than several devices). 
This then starts my arm twisting, by asking 
for another article. Many readers have con- 
sidered using PLDs, but learning and get- 
ting the necessary software is a big prob- 
lem. How about an article that covers Just 
what you had to do to develop the chip. How 
many failures did you have? What was the 
cost of the development system? Did you 
first do it in TTLs? Do you use PLDs and 
such for one up jobs? If so why? 

Well thanks again for the letter and keeping 
Z80 's alive Bill Kibler. 

User Interface Description 


The PT IDE802 performs all 16 to 8 bit 
conversions as required to make it com- 
pletely transparent to the user. Simply treat 
it as if the system was connected to an 8-bit 
IDE drive. 

16-bit disk VO is performed in MSB - LSB 
format. Prerecorded data such as ASCII char- 
acters in drive identification are thus read 
out in their correct order. Note however that 
the IBM PC stores data the opposite way. 

Sector data can be read out in any number of 
bytes, but should be written to the drive in 
even numbers only. The first byte in a word 


The Computer Journal / #70 

is stored in a holding register and is not 
written to the drive until the second byte is 
received. Any attempt to write an odd num- 
ber of bytes, will loose the last byte. 

Sector buffer I/O can be interrupted at any 
time to communicate with the printer with- 
out data loss, nor will any IDE task file read 
access upset a sector buffer data transfer in 
progress. A write to IDE COMMAND (port 
7) will however clear the sequencer, to guar- 
antee a clean start. 


CTINT occurs on a high to low transition on 
the ACK* input. An access to any CSI port 
to 2 will clear a CTINT. During CTINT, 
the open collector CTINT* output is pulled 
low. The inverted state of CTINT* can be 
read from bit 1, CENT STATUS 3. Trying 
to read it from CENT STATUS 1 will clear 
CTINT and return the bit as 0, regardless of 
what state it was in. 

IRQl, IRQ2 can be used as IDE and some 
other interrupt or as general purpose inputs. 
Their states are accessible on bits 0,2 in the 
CENT STATUS ports 1,3. INTl*, INT2* 
are open collector outputs reflecting the in- 
verted state of IRQl, IRQ2. 

All 3 outputs are open collector, and can be 
wire OR'ed into a single line. 

STB* output: Auto Strobe: 

A write to CENT DATA will assert strobe 
on the trailing edge of the write pulse. Data 
is latched and output on the leading edge. If 
the write pulse is too short to satisfy the 
printer setup times, the write should be pre- 
ceded by a write to CENT DATA 2 so that 
the data is already on the bus. A read from 
CENT DATA port will disassert STB*. 
That way it is not necessary to manipulate 
the control register in order to issue a STB*. 
Other printer control outputs can be set/ 
reset by writing to CENT CTRL 1, without 
affecting STB*. 

Auto Strobe example: 

OUT CENT .place data on bus 

OUT CENT DATA-0,data ;as5ert STB' 

IN CENT-DATA-0 ;disassert STB* 

Manual Strobe: 

STB* will follow bit in writes to CENT 
CTRL 3, and can thus be used as a general 
purpose output. All CENT DATA accesses 
should then be performed via CENT DATA 
2. Once latched, it can still be manipulate 
via Auto Strobe at a later stage. 

Uni/Bi-directional Mode 

The MODE pin is hardwired to select the 
required operating mode for the Centronics 
data bus CDO-7. 

MODE pin high: Bi-directional mode. 

A high to low transition on ACK* or INIT* 
will place CDO-l bus in Hi-Z as the pins 
become inputs. Once the edge is detected, 
ACK* or INIT* can be disasserted and the 
bus will remain in the input mode. Input 
data is not latched, so a read from CENT 
DATA or 2 will reflect the current state on 
CDO-7 pins. 

Writing to CENT DATA or 2 will place 
CDO-7 in output mode and latch the data 
onto the bus. CDO-7 will remain in the out- 
put mode and data from any subsequent 
writes will be latched to the bus. Auto strobe 
may be used if required. Reading CENT 
DATA or 2 while in output mode will not 
change that state, only return the data last 

The output mode is exited by a low pulse on 
the ACK* or INIT* pins. As INIT* is con- 
trolled from bit 7, CENT CTRL 1 or 3, it can 
be used to switch to input mode rather than 
waiting for an ACK* pulse. 

MODE pin low: Uni-directional mode. 

CDO-7 is always in output mode. Write to 
CENT DATA or 2 latches the data onto 
the bus until next write. Reading CENT 
DATA or 2 will return the data last writ- 
ten. The state of ACK* or INIT* is ignored. 

SPEAKER output 

This output is intended for a piezzo buzzer 
or other indicator. It is manipulated via the 
SPEAKER port and can be SET, CLEARED 
or TOGGLED. Writing to that port will not 
affect any other pin or operation, while read- 
ing from it returns the current contents of 


PT IDE802 is based on an EP1810 CMOS 

Package: 68 pin PLCC 
ICC: typically <100MA 

lOH/lOL: typically >I5 mA at TTL levels 

VIH/VIL: TTL compatible 

Brief timing specs: 

DBO-15 <-> DO-7 <-> CDO-7: 40nS 

A0.2 -> ABO-2: 35nS 

RD"AVR"/CS0'/CS1* -> HIOR'/HIOW": 35nS 

IRQl-2->lNTI-2: 35nS 

IOI6' valid to data (DO-7 or DBO-15) valid: 35ns 

RD* asserted to DO-7 output: J5nS (75nS ftom CSO'/CSl') 

DO-7 hold from RD* disasserted: 35nS to Hi-Z 
DO-7 hold after WR' disasserted: >5nS 
DBO-15 hold from WR' disasserted: 35nS to Hi-Z 
CSO'/CSl' stable prior to RD'/WR' strobe >5nS 
CSO'/CSl' hold after RD'/WR' strobe >OnS 

Detailed electrical and timing specs to be 

Generally, to calculate total IDE access time, 
add 75nS to the drive's specifications (ad- 
dress stable to read data valid). 

A 'SLEEP MODE' version is being investi- 
gated. This chip would require (2 octal) 
buffers to disable the CPU interface during 
sleep, when ICC should drop to below 100 

Notes on the CPU interface 

CSO* and CSI* should be connected to the 
corresponding pins on the IDE drive and be 
derived from an address decoder. It is advis- 
able to minimize decoding delays for these 

Neither the drive nor the PT IDE802 will 
react to spurious pulses on the select lines 
while RD or WR strobes are inactive. CSO* 
and CSI* could even be derived directly 
from two address lines where minimal de- 
coding is acceptable. RD and WR strobes 
should then be conditioned to occur only 
during I/O cycles. Conversely, active RD or 
WR's are ignored when CSO* and CSI* are 
inactive. Any spurious transitions on the 
RD/WR pins during active CSO* will 
misclock the sequencer. 

The IDE drive must be given sufficient time 
to validate its IOCS 16* output. RD/WR data 
may be compromised if that line has not 
settled at least 35 nS before any data access. 
The drive IOCS 16* pin is a function of its 
CSO* and AO-2 inputs. For that reason the 
select lines should be given a higher decod- 
ing priority over the RD/WR strobes. Refer 
to drive specs for actual delay. In any case, 
PT IDE802 require its select inputs to be 
stable during the entire RD/WR strobe. 

The bidirectional DO-7 bus is driven only 
during a RD* strobe with either CSO* or 
CSI* asserted. 

The two drawings are on page 20, at the end 
of Dr. S-100. I might note some interesting 
considerations in these specs, need for two 
byte writes, some sequence timing concerns, 
and chip selects (CSO&l). I don t remember 
if Tilmann 's interface has all of these con- 
straints or not Some of the handshakes can 

The Computer Journal / #70 


be handled in the BIOS, but others are hard- 
ware and as such mi^t limit the chip use- 
Jubtess on some machines. BDK. 

Dear Bill, 

Thank you for the sample issue. It sold me 
on your magazine. Please start my subscrip- 
tion and send the following back issues: 
Volume 2, issue 32, issue 36, and issue 65. 

I heard about TCJ from a friend that said 
Sinclair got the occassional mention. I started 
by buikiin a Sinclair ZX80 and have stayed 
with them. My main computer is now a 
Sinclair QL with a Motorola 24 MHz 68020 
with 4 MBytes of on-board 32 bit ram. Don't 
believe anyone that says the QL is dead! My 
QL is not the highest performance QL avail- 
able. The QXL is a 20 MHz 68EC040 with 
8 MBytes of 32 bit ram that lives on a board 
that plugs into any PC clone. High perfor- 
mance QLs also are available as plug-in 
boards for Atari ST and TT models. There 
also is a QL available as a software only 
emulator that runs on the Amiga. 

Would you mention the following support 
availaUe for Sinclair and Timex computers: 

IQLR (International QL Report). This maga- 
zine is in its fourth year and is steadily 
jpow i iig it* subscription base. The last issue 
was 65 pages. IQLR is published 6 times per 
year and has never been late. Contact Bob 
Dyl (401)849-3805 or write IQLR, 15 
Kilbura Ct. Newport, RI 02840. Subscrip- 
tion rate is S20 per year. 

Update fvfagazine is published 4 times per 
year. Xjpiite covers all Sinclair, Timex and 
(Cambridge computers. Contact Frank Davis 
(317) 473-8031 or write Update Magazine, 
P.O. Box 1095, Peru, IN 46970. Subscrip- 
tion rate is S18 per year. 

QBox-USA is a BBS supporting all Sinclair 
and Timex ccmiputers. QBox-USA has been 
(Mt-line 24 hours a day 7 days a week since 
October 1993. QBox-USA is a point off the 
Fido-Net in Europe. This means QBox- 
USA carries all the European Sinclair mes- 
sage traffic. Message areas include: Intcma- 
titmal QL, Minerva, Quanta, QBox and Spec- 
tnmi. You can communicate with users in 
the U.K., Germany, the Netherlands and 
other countries for the cost of a call to De- 
troit. There also is a healthy file area carry- 
ing the latest in public domain software. 
QBox-USA runs on a Sinclair QL with a 
USR 14400 modem. Callers from 300 to 
14400 baud are welcome. There are no fees. 
The number is (810) 254-9878. 

I'd also volunteer to answer any QL related 
questions your subscribers might have. I have 
16 years of experience as a computer service 
engineer for one of the largest computer 
companies. I've also fixed quite a few QLs 
so have the background to help others. 

By the way, CP/M runs on the QL under two 
different emulators. I have both of them but 
have not used them in quite awhile. I would 
be interested in seeing an article about CP/ 
M on the QL. 

Regards, Don Walterman, 331 Drace, Roch- 
ester, MI 48307, (810) 656^108 

Thanks Don for all that good QL informa- 
tion! Guess I will have to subscribe to IQLR. 
Since I like 68K systems and really always 
wanted to get a QL, you make me think I will 
find one to buy there. I am very interested in 
all the emulators and co-processor cards 
you listed. Seems like there could be a real 
long story about them all. How about it? 

I have run CP/M emulation on my Atari St 
and it works Just fine. The 68K systems are 
very good, in fact much better than most of 
the PC clone line for sure. Thanks again 
and keep us posted on QL news. Bill Kibler. 

To Whom It May Concern: 

I am enclosing a postal money order for the 
renewal of my subscription to The Com- 
puter Journal, beginning with #66. 

I am particularly interested in CP/M ar- 
ticles. I am using my original CP/M com- 
puter that I started out with, a Timex/Sinclair 
2068 v^th a Portuguese disk system. I also 
have 3 more of the same disk system as 
spares. It is like a C128, in that, it has 2 
other disk operating system: TOS (Timex 
Operating System) & the Spectrum disk OS 
- very similar to TOS, but for a ZX Spec- 
trum. I also have an Eagle, 4 Osbome-ls, 
a Tele Video TPC-1 (needs a boot disk), a 
C64 with the CP/M cartridge, a Sony SMC- 
70 that I picked up recently for $20 at a flea 
market (needs all cables, e.g., the video 
monitor cable) with the original "pinch-to- 
close" 3.5" floppies, an Osborne Executive 
in need of 4 disk rails & the lighted on-off 
switch, and an Industrial Micro Systems 
(IMS) S-100 that I need to take to the S-100 

I use dBASE n ver. 2.43* for my data base 
needs, WordStar 4.0 for my word processor, 
SuperCalc 2 for my spreadsheet needs, & 
IMP for telecommunications. I have many 
CP/M programs, however, I am currently 
looking for the following programs for sale: 

1) MicroSofl COBOL 

2) MicroFocus CIS COBOL 

3) CrossTalk (or XTALK) ver. 3.00 
or higher 

4) VEdit & VSpell 

5) The accompanying installation 
programs for ea I listed above. 

I hope you print this letter so that if there is 
someone out there that can help me, I would 
appreciate it. 

Thank You, Jay S. Siegel, 1274 49TH ST 
#821, BROOKLYN NY, 11219-3091 

P.S. You may , publish my address since it 
is a mailing address; it's not where I actu- 
ally live. This is NY, you know, & I wouldn't 
give,that out! 

I understand your concerns about the ad- 
dress Jay, and hope that someone helps you 
out. I might try Lambda Publishing first for 
those boot disks or programs. I do have a 
boot for the TPC-1 (I think). My mother in 
law had one and I keep copies of the disk in 
case she blew them up. 

I am rather interested in the portugese disk 
system, why and how? Just seems like the 
Sinclair machines are more popular than 
many think. Hope you find your software 
and thanks for writing. Bill 


TCJ needs your embedded 
story or project! 

Our readers are waiting to hear from 

you about how you developed that 

embedded project using 8051 or 6805. 

Used Forth, "C", BASIC, or assembler 

any language is fine, just tell us what 

happened, how you did it,and how it 

ended up. No project too small! 

Send those Ideas to: 

The Computer Journal 

P.O. Box 535 
Lincoln, CA 95648-0535 


The Computer Journal / #70 

The Z-System Corner II 

By Ron Mitchell 

Regular Feature 

ZCPR Support 

CP/M part 3 

Keeps Those Cards and Letters Com- 

Many thanks to Al Warsh of the Amstrad 
PCW SIG in CoUon Cahfomia for his 
recent letter. Al writes that it took him 
some time to get used to CP/M and that 
he's looking forward to learning more 
about ZCPR. He describes how he came 
by his copy of ZCPR3 through a deal 
with Jay Sage involving a surplus 
Amstrad PCW 8256s and a newsletter 
trade. All sounds quite familiar. The 21 
eight bit computers in my apartment here 
in Ottawa were acquired in similar fash- 
ion, more or less. 

Al sent along a copy of his latest Amstrad 
PCW SIG newsletter, a good read. The 
issue contains an adeptly chosen balance 
of hardware and software topics as well 
as a healthy offering of input from the 

It's a small world. One of the letters in 
Al's latest issue was from a gent I know 
very well out in Qualicum Beach, Brit- 
ish Columbia. If you know Canada's 
west coast at all you'll quickly pinpoint 
Qualicum Beach about half way up the 
eastern side of Vancouver Island. Beau- 
tiftil country. My parents live about 30 
miles north which means I get to pay a 
visit to this particular friend whenever 
I'm in the neighborhood. We've been 
computer buddies for some years, hav- 
ing as we do a common interest in an- 
other Z-80 machine, the Coleco ADAM. 

Thanks also to Fritz Chwolka who sent 
me an Internet E-mail saying, "Thanks 
for writing these articles in TCJ and I 
hope reading more from you.." 

Well Fritz, we'll give it a good shot and 
hopeftilly the begiimers will be able to 

follow and the old hands might have a 
chuckle or two watching me struggle. 
Fritz goes on to add that he is also a 
collector and a reader of Tilmann Reh 
on the Z280 system. 

Keep those cards and letter coming folks. 
I need your comments and 1 enjoy read- 
ing letters such as Al's. 

Past and Future Guidance 

While we're on the subject of newslet- 
ters, there is a whole series of articles 
prepared by Jay Sage that precedes my 
series here. TG/readers of long standing 
will know that the original Z-System 
Comer was ably prepared by Jay Sage. 
As was described in the last issue, Jay is 
one of the real pioneers of the Z-System. 
We'll be drawing liberally on his exper- 

If you have a CP/M or Z-Node BBS 
handy you might just find the earlier 
installments of Jay's work available as 
pubUc domain text files. If not, TCJ has 
back issues available (see pages 48 and 
49 for details). Jay's work begins in TCTs 
issue 25 and continues through to issue 
67. While I haven't checked for continu- 
ity, I assume that Jay was a fairly regular 
contributor because that's the way Jay 
does business. His original submissions 
appeared under the title, "The ZSIG 
Comer", and I notice that the third in 
the series was dated January 1987. 

You might find Jay's work considerably 
more advanced than the level we're pro- 
posing to follow here, but it is valuable 
stuff to read, and you'll do well to give 
it a try if you have it available. 

While you're looking for Jay's material, 
keep an eye open for something called 

the RCPM list. There you'll probably 
find the Z-NODE list close by. The 
RCPM list is a compilation of all known 
CP/M BBS's throughout North America 
and around the world. You'll find it 
helpfiil when looking for CP/M or Z- 
System software. The Z-NODE list pro- 
vides the names, locations, and telephone 
numbers of Z-System contacts around 
the continent and as far away as Europe 
and New Zealand. If you're looking for 
help, you might just find someone close 
by on one of these two lists. They have 
both been updated to September 1994. 

Down to business 

To quote author Richard Conn; (ZCPR 3 
- The Manual) "CP/M is an operating 
system: that is, a computer program 
whose function is to manage the resources 
of the computer and to provide services 
in response to standardized requests from 
applications programs (which manipu- 
late data in ways that serve the user's 
specific needs)." 

That's about as clear as it gets. It doesn't 
matter whether you are talking about 
CP/M, MS-DOS UNIX , 0S2, 0S9, or 
Rubberjunk's Bottleneck, that is what 
operating systems do. In the last issue 
(#69) we drew a small model of the CP/ 
M operating system; it looked as fol- 

High Memory 

CP/M 2.2 BDOS 

CP/M 2.2 COP 



The Computer Journal / #70 


I CP/M Buffers et al 


And that is the layout of CP/M 2.2 or as 
it's sometimes disparagingly known as 
"vanilla CP/M". Remember the tenns: 
BDOS is Basic Disk Operating System; 
BIOS is Basic Iiq>ut 0\dput System; and 
CCP is Console Command Processor. 
The area between memory location OH 
and OlOOH is known as page 0. A page 
is 256 bytes or lOOH bytes. 

ZCPR3 Syitem 

CP/M System 

Extended Fetfuns 


CP/M 2.2 Bt>OS 




ZCPR3 Baflen et al 

High Memory 


CP/M 2.2 BDOS I 

1 CCP+O800H 

CP/M 2.2 CCP I 



CP/M Buffers et il | 



The TPA is the Transient Program Area. 
This is the space which your application 
has availaUe. It ranges tyjHcally between 
48K and 61K depending upon how much 
RAM your system has. It can even be 
smaller than that. Note that an applica- 
ti(m that is going to obliterate or replace 
the CCP (either CP/M 2.2's or ZCPR's) 
had better make sure that it comes 
equipped with some other self-contained 
means of getting input from the key- 
board, or fiom wherever it's designed to 
get inpat It had also better replace its 
divots when it is finished; ie. replace the 
CCP or re-boot the operating system. 

The difference as is obvious from the 
diagram is an enhanced Console Com- 
mand Processor and the extended fea- 
tures in high memory. This is what we 
mean to explore. 

Begin with the BIOS 

To complete our discussion of the rock 
bottom basics, let's return for a moment 

to the 'computer resources' that Richard 
Conn was talking about. What are they? 
We hsted them in the last installment: 
memory, processors and processes (run- 
ning programs), devices, and informa- 
tion. Remember that it is device man- 
agement where CP/M excels and that 
device management is performed by the 
BIOS. Control of and communication 
with disk drives, keyboards, printers, 
modems, interfece cards, and other won- 
derful widgets are taken care of, boss. 
You don't have to worry about a thing. 
Amongst the functions performed by the 
BIOS there are the following, (and I'm 
quoting Coim again because it's the fu-st 
place I've seen it described in under- 
standable terms): 

1. Initialization functions; cold boot, 
warm boot, (setting preliminary values 
in strategic memory locations for later 
use, defming pointers to various impor- 
tant places in memory); 

2. Character Input/Output fimctions; (in- 
cludes status checks - got anything for 
me )- console, printer, and auxiliary in- 

3. Disk Input/Output Functions; 'hom- 
ing a drive', selecting a drive, selecting 
a track and sector, reading and writing a 
block of data, selecting a memory ad- 
dress from which to get it or at which to 
put it, and some mystical function called 
'logical to physical' sector translation. 
(About this latter we shall have to learn.) 

Busy fellow this BIOS. 

I don't want to get hung up on this stuff. 
Everything I've been talking about so 
far is located in the first 5 pages of 
Richard Conn's book and it seems like 
we're not making much progress. We 
certainly haven't said much yet about 
ZCPR3 or Z-System except to draw a 
picture of it. In your own basic books on 
CP/M you're likely to find similar de- 
scriptions of how various elements of 
this fascinating piece of programming 
fit together. My purpose here is only to 
provide a broad brush background of 
where Z-System sits. 

It is in feet, as we have said, an en- 
hanced Console Command Processor. In 

our last installment we said that 'va- 
nilla' CP/M knows only six words: DIR 
thing else has to come from a transient 
command or program. 

What's Wrong with CP/M? 

And while we're rurming down 'vanilla' 
CP/M, let's really do a number. 

1) Each time you change disks, you have 
to 'warm boot' the system before you 
write to the new disk, that is you must 
press <CONTROL> C or an infuriating 
error message will result, usually where 
you least need it. 

2) There is no standard method of clear- 
ing the screen from the operating system 
level. In some cases it's <CONTROL> 
L, in some cases it's <CONTROL> Z. 
Who knows? 

3) You can't assign names to user areas. 

4) Each time you obtain a new piece of 
software for your system you have to 
configure it specifically for your particu- 
lar setup. In the pubUc domain world, 
you'll be lucky to get the Install file 
along with the main program, and that 
will lead to trouble. 

5) You caimot set a search path. The 
program you call up had better be in the 
drive and user area you're logged into or 
the system won't find it. 

6) Progranmiers have no access to flow 
control at the operating system level. If 
you're assembling the source code of a 
program and that source contains an 
error, there is little point in carrying on 
with the linking and loading of that file 
The resulting .COM file probably won't 

7) Shells, scripts, alias's? What are these? 

8) With 'vanilla' what you see is what 
you must carry with you. There is no 
possibility of configuring the system to 
the speciJBc requirements of the job at 

9) No multiple command lines. 


The Computer Journal / #70 

10) No access to a vast and comprehen- 
sive set of tools available under Z-Sys- 

There's a payoflF all right. Now I am 
prepared to grant you that many of the 
points in my foregoing list of ten are 
things that only a CP/M programmer 
would appreciate. If you're going to use 
CP/M to run applications without look- 
ing under the hood, then you might miss 
the importance of some of this. So let me 
describe some personal experience that 
will perhaps pave the way for a more 
positive description of where we're go- 

Home of Micro's 22 

I have a collection of old computers. 
Several of them are CP/M compatible. 
There's an Osborne 1, a couple of Com- 
modore 128's, an Apple 11, a PMC 101 
Micromate, five Coleco ADAM's, and a 
partridge in a pear tree. There's more 
than that lining my wall space but they're 
not CP/M machines so they don't count. 

On the ADAM I had the benefit of a 
little help from my fiiends, who made 
me what I am today. (That still has them 
worried.) The advent of a CP/M 
workalike called TDOS (Tony Morehen 
and Guy Cousineau, AJM Software ) 
spoiled me rotten when it came to CP/ 
M. All of a sudden 1 could clear the 
screen of my computer with a simple 
CLS command. I could copy files with- 
out invoking C0PY.COM or the dreaded 
PIP.COM. There were many many utili- 
ties that came with this thing, utilities 
which I've since come to recognize as 
part of the Z-System package. 

So I got used to all of this and the house- 
keeping of my CP/M collection became 
a pleasure rather than a chore. Then out 
of the blue, somebody put a Xerox 820- 

II on my desk at work (this was a few 
years ago), and I suddenly began to ap- 
preciate the value of these Uttle enhance- 
ments that had been put at my disposal. 
The Xerox was 'vanilla' CP/M 2.2 and 
stood out in stark contrast because of 
what it couldn't do. The Osborne was 
the same type of experience. Operating a 
pair of 180K (give or take) disk drives 
without a search path was a real chal- 

lenge. There's httle enough disk space 
(when you've been used to a 20 or 40 
MEG hard drive elsewhere) and you need 
a 'if-the-program-isn't-here-then-go- 
look-there' capability that the search path 

There was also the benefit of being able 
to operate in a uniform fashion across 
several different machines. The Osborne 
in my collection has had more of a work- 
out since NZ-COM arrived in this apart- 
ment than ever before. It sits by my easy- 
chair in the living room where I can fell 
asleep and compute at the same time. 
Ain't life grand! 

Tall Tales and TCAPS 

One of the more sizable advantages of- 
fered by Z-System is its ability to include 
right in the operating system an envi- 
ronment descriptor or terminal capabil- 
ity. Shorten that to TCAP. The various 
fiinctions of a video terminal, as you 
may know, are controlled by a series of 
codes usually consisting of the 'escape' 
character plus one or more characters 
sent either in ASCII or HEX. On the 
Cybemex XL-87 attached to my PMC 1 1 
Micromate for example, the code to clear 
the screen is IB 45 hex or <ESCAPE> 
E. On the Coleco ADAM attached to my 
Hazeltine 1510 the same operation is 
accomplished by sending a 7E IC hex or 
~ <CONTROL> \. On the Commodore 
128 (Terminal emulates a Lear Siegler 
ADM 3 A) it's a 1 A hex or <CONTROL> 
Z. Three different terminals, three dif- 
ferent ways to clear the screen. If I wanted 
to run a CP/M application on these three 
computers I would have to either patch 
it with the appropriate codes or use 
ML0AD.COM with a suitable overlay. 
Each new application to be run on any of 
these machines would have to be simi- 
larly installed. The same applies to print- 
ers which also perform various fimc- 
tions such as holding and underlining, 

The Z-System TCAP takes care of all 
that. You install your terminal only once 
and when you run Z-System compatible 
software from then on it, there is no 
installation required. And that's only 
the beginning of the payoff. 

As these issues unfold we'll be explor- 
ing the many other benefits that Z-Sys- 
tem has to offer. I presently have Z3PLUS 
installed on this PMC 101 Micromate 
and NZ-COM installed on Ossie the 
Osborne. The installation procedure went 
right by the book with Ossie. With the 
Z3PLUS version there was one gUtch 
that the book didn't tell me about, and I 
want to check that out with Jay Sage 
before proceeding further. I'll get into 
details on that in the next article. 

I'd like to finish this article with a little 
more philosophy. I'd like to let you 
know exactly where I'm at in terms of 
my knowledge of CP/M and Z-System 
so that there'll be absolutely no misun- 
derstandings about what you're getting 

I'm writing this from the perspective of 
one who is discovering it all for the first 
time. That's the way it is. The Z-System 
has been resident in this household for 
only a few months, and sooner or later 
the experts following these articles are 
going to call my bluff. I'll coimter that 
threat before it even get's here by saying 
that I certainly wouldn't want to be mis- 
taken for an expert. We've covered this 
ground before. 

There is lot's of help available. I have an 
able group of CP/M 'gurus' right in my 
back yard. Ian Cottrell has been a good 
friend for many years. Many of you will 
recognize him as the co-author and 
present guardian of the PBBS 5.x BBS 
program. lan's INFOCENTRE board is 
the local Z-NODE which offers an im- 
pressive list of software to chew on. Then 
there's my long time fiiend and fellow 
ADAM owner, Guy Cousineau, who's 
implementation of CP/M 2.2 on the 
Coleco ADAM, known as TDOS, had 
me enjoying the benefits of Z-System 
without really knowing it. As previously 
said, it's only when I return to a CP/M 
machine that runs 'vanilla' that I realize 
how far we've come. There are others up 
here upon whose considerable expertise 
I can draw. 

Further afield, but only as far away as 
the nearest FIDONET or INTERNET 
drop there are many many experienced 
Z-System and CP/M people who are more 

The Computer Journal / #70 


than willing to lend a liand. As you 
incr ase your contacts with these people 
on the CP/M Tech Echo and 
CO /IP.OS.CPM you'll find them 
frie idly and helpful. Don't be afraid to 
ask questions. 

Speaking of which, it seems appropriate 
to finish this installment with something 
of a quick and dirty shopping list. What 
do we want to know? 

You're likely to find me wandering all 
over the place. I was leafing through the 
Z section of lan's BBS last night and 
found a literal ton of programs waiting 
to be written about. Each could generate 
it's own article about some aspect of Z- 
System and that would take more than a 
lifetime. In amongst the programs were 
the earlier installments of the Z-System 
Comer by Jay Sage as aheady mentioned. 
I took a look at the first three and real- 
ized how much of this I don't know yet. 
Jay introduces some of the new Z utili- 
ties that were being written in and around 
1987 and describes techniques for speed- 
ing up the performance of Z-System 
through strategic placement on the stor- 
age media of the various elements. Then, 
at Ian Cottrell's place last week, he 
showed me the power of an 'alias', a 
string of several Z-System commands 
contained in a single .COM file and 
usable simply by typing one command. 
There is much to learn. 

The value of it all will depend upon 
what you're doing with your computer 
and what capabilities you need from your 
operating system. We'll have to explore 
what benefits there might be for those 
who simply want to use one or two ap- 
plications such as word processing per- 
haps or a spreadsheet. Those making 
use of various disk maintenance and pro- 
gramming utilities might stand to ben- 
efit to a greater degree, Those interested 
in assembly language programming and 
the development of applications will be 
loddng for a completely different set of 
capabilities from Z-system. 

How do you rate these things? Improved 
efficiency? Doing a particular comput- 
ing job in less time with fewer steps? A 
more comfortable feel to the user inter- 
face because you've designed it your- 

self? Greater transient program area 
made available by not having to use space 
for program routines that you don't need? 
The ability to change your operating 
system on the fly? Designing your own 
tools to get the job done? This is only a 
small portion of the list of benefits 
claimed for Z-System. 

Upcoming articles will describe my own 
experiences with the product. So far I've 
removed it from the box and, as men- 
tioned, have installed it on two comput- 
ers. That's the sum total of my achieve- 
ment so far. Beginning with the next 
installment, we're actually going to start 
using Z-System. We'll install the TCAP 
for both NZ-COM and Z3PLUS, and 
take a look at organizing a system disk 
for our Z-System work. 

In the meantime, here's the quick and 
dirty shopping list that describes in very 
rough fashion what we can hope to ex- 
plore over the next few sessions. 

1) What is an alias? 

2) What is a shell, and what fimction do 
shells perform? 

3) There are all sorts of acronyms to be 
mastered; two of the most common are 
the FCP and the RCP. What do these 
stand for, and how do these elements of 
Z-System contribute to it's power as an 
operating system. 

4) We're going to make a startup disk 
for both Z3PLUS and for NZ-COM. 
What do we want on this disk. Another 
way of putting this question would be 
that you're marooned on a desert island 
with your favorite computer and only 
one floppy disk. What would that disk 

5) How does one go about installing Z- 
System, and what are the pitfalls to watch 
out for? 

6) What do the programs ARUNZ and 
SALIAS do? What other utilities are 
available under Z-System? 

7) What is the effect of Z-System on the 
availability of transient program area? 
What is the cost in terms of overhead? 

8) How can Z-System be configured for 
different jobs? 

9) What are the advantages of flow con- 
trol, and how is it achieved? 

10) What about multiple command hues? 
What good are they, and where are they 
most frequently used? 

There are many many more questions 
that we'll be dealing with in future ar- 
ticles. These 10 are not mentioned in 
any sort of order, and they'll be an- 
swered as we get to them. 

Do you need 

Micro Cornucopia Disks? 

Echelon Publications? 

Boot Disks? 

Disk Copying? 

Lambda Software Publishing 

can now supply reprints of 

Micro Cornucopia Magazine, 

Kaypro Disks, Boot disks, CP/M 

2.2, ZCPR and CP/M programs. 

Kaypro disks $5.00 

all 49 disks $200.00 

Big Board disks $5.00 

all 30 disks $100.00 

Catalog of disks $5.00 

Disk Copying $10.00 

MicroC reprints $8,00 

CP/M 2.2 $25.00 

CP/M Plus $25.00 

Spellbinder v5.3H $60.00 

Echelon Publications $ 1 5 . 00 

Four or more $10,00 

User Guides:ZCPR 3.3, Z- 

System, ZAS/ZLINK, ZDM/ 

ZDMZ/ZDMH, JetFind, and 

many other Manuals. 


Lambda Software Publishing 

149 West Milliard Lane 

Eugene, OR 97404-3057 

(503) 688-3563 


The Computer Journal / #70 

Dr. S-100 

By Herb R. Johnson 

Regular Feature 


Letters In The Mail Bag 

"Dr. S-lOO's pre-Winter column" by 
Herb Johnson (c) Oct 1994 


A lot of Internet messages appear in my 
column, partly because my volume of 
US mail has declined a bit. Mail should 
pick up in the winter. This column I 
follow up on interests in my S-100 IDE 
interface from last issue, and a bit on the 
Western Digital hard disk interfaces from 
a knowledgeable reader. A few of my 
colleagues get some press for their help 
(and probably to you in the future), and 
I tell you who has given me what lately, 
and how you can get yours. 

(By the way, let me know if you like 
reading my correspondence, or want 
more hardware-packed articles, or what. 
You know where I am! Also, I apologize 
for any spelling errors in this issue's 
column, but my spelUng checker stops at 
every 5th word, like IDE, net, 
CPMTECH, etc..) 


I'm getting more and more traffic on the 
Internet, after I armounced my netmail 
address last colunm. I've also noticed 
the annual decline of mail in the FidoNet 
echo area CPMTECH. At least, I hope it 
is only the summer slowdown and not a 
loss of interest! People are busy playing 
in the summer, and only get back to 
their basements - 1 mean their computer 
workshc^s - in the winter after the chores 
of fell are completed. 


As always, please include your network 
address or BBS location in your written 

or phone correspondence. This will al- 
low us to respond to your requests rap- 
idly and cheaply. And, if you use an 
address of any sort from my column, 
please note the source! And, if you want 
our correspondence private, please tell 
me so: trust me to use some discretion in 
quoting you and in my comments. 

Denis J Carlos of Newman CA has a 
number of California Computer Systems 
cards among others to sell that "would 
be nice to see put to use again." They 
include 16k static RAM, Buss termina- 
tor, 4-port serial, floppy and Z80 by CCS; 
a George Morrow HD (hard disk) con- 
troller and a Godbout 18 slot buss board. 
Contact him for more information. 

Trades and orphans 

Many people have S-100 systems that 
are about to be dumped. Perhaps you are 
one of them: the spouse insists that the 
garage be used for cars instead of com- 
puters; or the desk be cleared for the 
"new" computer; or the spare bedroom 
be used for a precious collection of natu- 
ral disaster newspaper clippings instead 
of your computer museum. Maybe you 
simply want to "pass on" your system to 
someone who will learn from it. 

The Dr. gets a number of calls of this 
sort, and tries to accommodate when he 
can. Jim Briggs of Mt Laurel NJ called 
me last month, to try to "place" his 
Compupro 8/16 system in a good home. 
And it is quite a system. Many readers 
may recognize this system as the "prede- 
cessor" oftheHeath/ZenithZ-lOO which 
was an unlicensed copy of the 8/16. It 
has an 8088 and an 8085 processor and 
runs both MS-DOS and CP/M. The Z- 
100 is one of the more popular "bridge" 
systems of the post-IBM PC period. 

bought in large part by the miUtary for 
base use and "dumped" in surplus over 
the last few years. 

Jim's S-100 system includes some nice 
color video cards and a pair of 8" Qume 
drives, and included both software and 
manuals. It is rare to be offered such a 
well-documented system. Jim was so 
pleased to be able to provide it to a 
knowledgeable person that he offered to 
deliver it the day of his call! Well, the 
Dr. knows when to ACCEPT a house 
call! Jim arrived a few hours later, not 
only with his system but with an Epson 
LX-80 printer and a Canon bubble jet 
color printer! When the cold of winter 
sets in, I'll have more time to describe 
this system in detail. As it is one of the 
most popular and powerful S-100 sys- 
tems of its time and deserves a full re- 

For the reader, I would suggest one way 
YOU can find a good system is to simply 
place an add in the computer section of 
your local paper. Note that you will pro- 
vide "a good home" for a CP/M system 
or old computer. You should be specific 
that you don't want an IBM or Mac or 
Commodore, etc. as your tastes dictate. 
This will save you from many calls. Don't 
think of this as begging, but as a kind of 
"adoption." You might mention "don't 
take it to the curb" too. 


My colleague David McGlone of Lambda 
Software and I often assist each other iu 
hardware and software for our client 
David also had a chance to "rescue ' 
several systems and offered me a share 
in the loot - 1 mean the to-be orphaned 
systems. As a result I will receive a 
Compupro 68000 card and some other 

The Computer Journal / #70 


Compupro docs and disks. David is 
strictly a Z-80 kind of guy, and I am an 
S-100 specialist (all doctors are special- 
ists these days) so our interests overlap 
occasionally. David is a good resource, 
as is his magazine The Z-Letter which I 
recommend to everyone. 

Another colleague of high standing in 
the classic con:q)uter community is Lee 
Hart, "the Heathman," who is also a 
regular letter writer to TCJ. While as- 
sisting me with a Z-100 customer, he 
sent me two Zenith binders of documen- 
tation on CP/M 80 and CP/M 86 for the 
Z-100. And, he has a lending library of 
books and documentation on these and 
many other systems, as well as Z80 and 
other processors. His fees are extremely 
modest: just a few dollars plus postage. 
If you need some more information on 
classic systems, particularly the Heath/ 
Zenith line, send him a request and he'll 
send you a list of bodes and stuff for 
loaa (You shoukl throw in a dollar or 
two to cover his costs. Mention my name 
so he knows who is buttering his bread.) 

S-100 IDE fan mail 

As I write, the previous issue of The 
Computer Journal has only been out a 
few weeks. Even so, I've received a few 
letters and netmail on the S-100 IDE 
design by Claude Palm of Palmtech in 
Australia. I've had quite a net corre- 
spondence with John Wilson 
<> about IDE and S- 
100 stufC and I've mailed him a copy of 
the IEEE-6% specification for the S- 
100. John had developed an IDE for the 
IBM (?) and has REALLY classic com- 
puters going bade to the PDP-1 1 ! (more 
on that later). One of the things I enjoy 
about my colurtm is that it introduces me 
to a variety of active hobbyists and to 
early developers of classic systems. 

One message of note is fi-om Tilmaim 
Reh, TCJ's correspondent from Ger- 

" ...reading your column in TCJ #67, I 
think you should consider the following. 
When you are thinking of an IDE inter- 
face board for the S- 100 bus, you should 
carefully check if the single-chip solu- 
tion using the PLA of the Australian 

[Claude Palm] also is the cheapest solu- 

In my experience with circuit design, it 
often has proved that a circuit with more 
but cheap TTL chips was much cheaper 
than the highly integrated (and more 
elegant) solution. When having a look at 
my IDE interface board for the ECB bus, 
I could also have done it with a single 
PLA (except for the bus drivers), but the 
TTL solution is much cheaper. When 
using GAL [gate array logic, another 
programmable logic chip class] I nor- 
mally use the cheap standard parts like 
16V8 and 20V8...even a 22V10 is much 
more expensive and might not compen- 
sate [for] several more TTL's! 

Some more hints on planned options: If 
you want to implement an FDC, use the 
SMC FDC37C65C. I can recommend it 
very much, and it woiks up to 1 Mbps 
data rates (as used in the ED drives and 
disks [example: the 2.88 Mbyte IBM 
floppies]. However, don't let the FDC 
select the four drives, use an external 
TTL register chip instead! If you need 
details, contact me freely. 

For the serial interface, you might con- 
sider using an 82C452 chip which is 
commonly used in PC's. This is very 
cheap, and will do for most purposes. 
Compared to other cheap devices, it has 
two on-chip programmable baud rate 
generators. If you want to [instead] do 
the best, use one of the Zilog SSC family 

In any case, design the decoding cir- 
cuitry so that each additional interfece 
might be built up optionally. This way, 
you keep the cost low for those who just 
want the IDE interface." 

[Tilmann is of course correct: given the 
large "real estate" of the S-100 card, and 
that most printed circuit board shops 
charge by the square inch and not by the 
hole, a collection of cheap chips is 
cheaper than one expensive chip. Of 
course, Claude was designing for ^ce 
rather than cost and so the single-chip 
solution was best for him. Nonetheless, 
his choice for prototyping was the S-100 

(BTW, Tihnann also reminds me that 
my previous correspondence was from 
"Emmanuel Roche" and not "Roche 
Emmanuel", who has the habit of swap- 
ping his first name and surname in his 

Another bit of Internet traffic on the 
SIOO-IDE comes from Patrick Logan 

"Herbert, 1 am good for 2 of the litUe 
darlings. How do you want payment ? 
Instead of a SlOO board, how about a 
generic board that mounts to the IDE- 
drive and cables over to the CPU-board 
? or can be mounted to a SlOO board ? or 

Yeah, there's only a couple of people 
right now suggesting that they will have 
a "small" or "generic" IDE board avail- 
able very soon now Seems there is 

always someone "out there" who has 
something that can be adapted, but some- 
how it never happens. The fact is, it is 
hard to make SPECIFIC hardware and 
especially software "general." Ask any- 
body who has done Z-system develop- 

There's one more dance in the old girl 
yet.. .and yet another fan of the 'IDE is 
Bob Finch <bfinch@asp.> 
who writes in an interesting style which 
I will quote unaltered: 

"wow!!!...i am impressed with the stuff 

in issue 69 of tcj to wit;.... is this chip 

available in more generic flavors for z- 
80 NON-SIOO systems.. .if so what are 
the particuulars ...and 

what about software etc i have a single 

board with scsi interface. . ..i am currently 
ruunning my de-block into a adaptec 
4000 (a) board and formatting ril drives 
as sif they were mfin.... 
BUT ide may be option to seriouly 

consider running zcpr3 something, of 


nice columm and keep up the gud 

work...tjc is an interesting mag but 

sometimes i want mor e COMPLETE 
stuff. ...i know this can be difficult for 
any number of reasons, and i do sin- 
cerely hope tcj doesn'tt sell out on either 
6800 or z:-80 coverage to the pc et al 


The Computer Journal / #70 

please taae care es best regards baab" 

[After a quick and sharp reply by The 
Doctor (that's me) that suggested that he 
was looking for a simpler kit than I had 
considered providing, and what does he 
really want anyway. Bob writes:] 

"thank you for the quick reply!... so, 
anyways, i really didn't mean to leave u 
with a wrong impression to wit; yes some- 
times a 'kit' would be easier, sometimes 
just software and hardware as compo- 
nent items is sufficient, sometimes just 
software, uh (at least for me) seldom just 
hardware so i am looking at soft- 
ware, and was writting u to find out 
about chip availabiUty (and styles), as 

well as software availabiUty AS PER 


as for my comment about sometimes 
things are skimpy in tcj it was NOT 
directed at you. your collumns are ex- 
ceptionally interesting, and I have no 
complaints, in fact i have no complaints 
about anyone's col., but sometimes the 
authors DO assume that hardware or 
software is trivial, it may be to them, but 
not to some readers, puesdo code is often 
times not enough, sometimes is, and 
because magazines such as tcj have to 
serve a larger interest, col. size is lim- 
ited, i guess my concerns are related to 
a lack of space, which, by it's very na- 
ture, is not a critique applicable to the 
authors so please don't take my mus- 
ing too seriously 

finally yes ide could well be more attrac- 
tive to me i don't know, but seriously 

doubt that my adaptec 4000 board is 
fiilly compliant with modem scsi drives 
(or vice versa) and that it wouldn't just 

be easier to meld something else in i 

haven't really checked, but alot of water 
has gone under the bridge since i put 
this together in the very early 80 's 

again i have NO complaints of any na- 
ture with you or your column, it's con- 
tent or otherwise, and YES i would be 
interested in this new development of 
ide drives for z-80's and z-sys (or cp/ 

m) please do continue with software 

and statemachine info etc and thanxs 

for being a resourse... 


bob finch (baab)" 

[Does anyone recognize the literary style 
of Bob's writing? The subtitle gives a 

Bob makes the same point that Bill Kibler 
makes to me: everything MUST BE 
EXPLAINED! New readers, or old read- 
ers who lack experience, or just plain 
confiised readers, need to know the de- 
tails! And, readers with one system may 
greatly desire the featiues in an article 
on another system but will have great 
difficulty adapting it over if details are 
lacking. I try in PRIVATE conespon- 
dence to make up for what lacks in my 
PUBLIC writing, if only to save space; 
but we can all do a bit more. 

So far these are the nibbles of interest in 
IDE, but I have had no flood of mail or 
messages! If you want to see anymore of 
this project, call or write or netmail me 
NOW! Even with a few requests, I hope 
to provide chips and docs to those inter- 
ested even if I don't publish the rest of 
this project. 

More info on Western Digital control- 
lers: pre-IDE? 

lohn Baker <> 
replies to my previous column's notes 
about Western Digital (WD) hard disk 
controller cards among other's: 

"I just received issue #69 of _TCJ_ and 
I was a tad concerned that you assumed 
that the WD-1002-05 was in any way 
related to SASI/SCSI. [I had presumed 
it was a SASI controller, like some of the 
Adaptec and other controllers of the era] 
The WD lOOx-yyy boards bear absolutely 
no resemblance to SASI/SCSI. I've read 
a number of comments from people in 
various fora [forums?] in which they 
assert that these boards are SASI. 

The WD lOOx boards are found in a num- 
ber of classic computer systems, such as 
the Kaypro 10, Televideo 80xH, and 
Epson QX-10 (via Comrex Comfiler). 
They are also the original hard disk con- 

trollers developed for the IBM PC's. 

A few notable variants: 

WD 1002-05 — stand-alone hard disk 
and floppy disk controller card uses 
WD 10 10 HDC and WD2797 FDC 

WD1002-HDO — "Hard Disk Only" 
controller card, like above but without 
FDC circuitry (not installed). These are 
the boards most commonly found in 
Kaypro and Epson. 

WD1005-yyy etc. IBM PC-bus version 
of the above. Much of the trouble that 
users experience with modem IDE drives 
comes from some limitations of the 
WDIOIO HDC used in these boards. 

Yes, the WDlOOx series of hard disk 
controllers were the fore-mnners of 
today's IDE hard disks. In fact, the 
WDlOOx Task File Interface is nearly 
identical to the IDE Task File Interface. 
The only changes are re-assigrunent of 
some bits in the Size/Drive/Head regis- 
ter and that all 8 bits of the Cylinder 
High register are available for IDE. 

As you may recall from my traffic in 
CPMTECH this summer, I explained 
this to several people. I have an IDE 
drive running on my Epson QX-10 and 
the only significant BIOS modifications 
required were to increment the sector 
number by 1 and explicitly set a 1 -sector 
transfer. All other code is the original 
routines for the WD1002-HDO that was 
supplied by Epson. 

Remember, WD-lOOx-yyy is NOT SASI/ 
SCSI, but IS very close to IDE... 

Take care." [John's message "signature" 
follows as a matter of interest:] 

John D. Baker ->A TransWarp'802'd 
Apple lit CardZ180 Z-System nut // 
BBS: JOHN BAKER on PIC of the 
Mid-Town [(713) %1-5817] 1:106/31, 
Z-Node #45 [(713) 937-8886], The Vec- 
tor Board [(716) 544-1863] 

(hurmmph!) Well, I guess I stand ror- 
rected. By the way (BTW), IDE at the 

The Computer Journal / #70 


REGISTER and COMMAND level is a 
"stretch" of the Western Digital floppy 
disk register and command set. 

More Classics: the PDP-11 

Nfy day job in the 1980's at Eastman 
Kodak included some work with Digital 
Equipment Corporation PDP-11 mini- 
computers and VAXes. The 11 's had 
been around for several years and I used 
them in college too. They have a straight- 
forward instruction set, 16-bit registers, 
and good amounts of memory. Peripher- 
als were memory-mapped, and in fact a 
Mot(»ola processor programmer would 
find a lot of PDP 1 1 code and practices 

As John Wilson wrote me about S-100 
and IDE stuff, it emerged that he has 

been working on a PDP-1 1 simulator on 
the IBM-PC for some time. It supports a 
number of serial ports for terminals, and 
has been running some of the operating 
systems by emulation. It supports 8-inch 
floppy drives with the Compaticard 
floppy controller. 

Interested? Contact John or download it 
from the Internet: John says, "Well it's 
free, they can snag it from, pub/ibmpc/emu- 
lators, filesell.comandell.doc, when- 
ever they want (starting with the next 
version it'll be ell.exe, I ran out of 
space). If you are interested in commer- 
cial use "for running your factory off an 
old PDP 1 1/45" as John suggests, he is 
interested in providing customer sup- 
port for a fee. I asked John about writing 
a TCJ article: send him encouragements 
(me too!). 


John Wilson <>, 11 

Bank St Troy NY 12180. 

Tilmann Reh <tilmann@hrz.uni->. 

David McGlone, Lambda Software - see 

his ad this issue. 

Lee Hart 


4209 France Ave N. Robbinsdale MN 


Dennis J Carlos, 568 Real Q, Newman 

CA 95360. 

Patrick Logan 


John Baker <jdb8042@blkbox.COM> 

Bob Finch <> 

Heib Johnson 


Reader To Reader Continued: 



Z80 CPU 







w . 

EM • 







Design example to interface the PT IDE802 with a Z80 CPU. 










IKIT" - 




M! - 
ABl - 
ABO - 

PT IDE80? 




^ o 









°"' LOU 


— D i2 — ' 







PT IDE802 Block Diagram. 


The Computer Journal / #70 

The European Beat 

by Helmut Jungkunz 

Regular Feature 

All Users 

An AMSTF?AD Expert? 

Helmut sent me this first half by E-Mail just after I took #69 
to the printer. Since I think it helps explain about his back- 
ground, here it is. BDK. 

How to become an expert 8-bit idiot 

I still remember the time, when the image of a computer still 
related to ENIAC or monsters of that size. 1 also remember 
leaving my home town to settle out for a new life in the big city. 
After four weeks of jobbing in a carpet company and endless 
jam sessions with fellow musicians (I wanted to become a pro 
then), I got this job with a certain American company, Digital 
Equipment Corporatioa 1 worked as a stock clerk there, when 
soon I detected my abihty to memorize all the part numbers 
involved, in fact, even today, 21 years later, I remember a 
number like 70-6267-01 for the "Head, Flying Upper" and 1 
was one of the best and fastest databases around. Before I could 
turn my head to say no, I foimd myself in a position as a leading 
stock organizer for all Germany. I even flew to a central 
European meeting in Amsterdam. Mind you, 1 still didn't 
know what they needed all these parts for, I just had some 
vague ideas, how Teletype devices could be used for data entry 
and output. 

This tells the basics of the rest of my "computer career". I 
always worked high above my actual knowledge level, creating 
fimny situations sometimes, when "colleagues" started to throw 
their vocabulary at me, expecting me to fiilly comprehend 
everything they said, maybe even give them some advice! 

When we had a sudden vacancy in our flat, a guy moved in 
with a Sinclair ZX81. Boy, was 1 impressed, how they man- 
aged to get such a fantastic flight-simulator on a tiny little 
machine like that! The last computer I had seen before that, 
had been a PDP-8e, quite a monster, like a refrigerator with 
drawers and dozens of toggle switches. 

After a couple of months, the guy moved out, but my contacts 
with him survived. He advised me to buy my first home 
computer, the AMSTRAD CPC 464, like you might have read 
before. Again, here I developed a video interface to connect the 
CPC to a colour tv through stealing some ideas from a techni- 
cal magazine's test generator. I wrote articles on subjects that 
I had to dig up information to know the basics. 

This is maybe not too serious, but there was a certain side effect 

to that: in order to stay honest, 1 tried my best to keep the 
information authentical. This again forced me to read a lot and 
get deeper into many subjects, than 1 would ever had without 
the articles. After a short while, 1 was writing more articles on 
"monitors", "the video side" and so on for a computer mag. I 
volunteered to test listings of readers (my BASIC knowledge 
was still very limited then) and even managed to improve some 
of them after a while. I wrote articles for our club magazine and 
soon advanced to the head of the club. 

In the meantime, I got to test hardware for the CPCs. I used my 
mere likes or dislikes to judge the handiness of some gear, 
being fiilly aware, that exactly that view served the readers 
most. Of course, again, I learnt increasing amount offsets, and 
could be of great value in the later development of new hard- 
ware for the CPC. 

All of a sudden, 1 was presented with a dying magazine 
thatdidn't have enough people to properly support the readers. 
So they asked me to assist with this job. As always, things 
spiraled out of hand and I ended up answering all the letters tc 
the editor. Sometimes I was completely lost as to what the 
people wanted to know about. I spent lots of time on the phone, 
but there were few people who knew as much on the subject as 
I did. Now this was a new situation for me. I had become a 
specialist, not being aware of it. While not being able to 
understand the more sophisticated BASIC programs I received, 
I spent much of my time reading the documents from some of 
the SIG/M public domain discs i had purchased. After all, I 
found it much more interesting to read about this ZCPR thing 
they got wild about. I even got more information from the 
MORROW OWNER'S REVIEW (MOR), when I read articles 
like "Tools for Tyros" or "Forever Z". Still, I wasn't even able 
to properly use MOVCPM. The tool I mostly used, was DDTZ, 
a German Z80 version of DDT, with a string query option and 
a write function built in. 

Thus, I garbled up several versions of PONG, ALIENS and the 
like. I don't know why, but our club members started to talk 
about me as "public domain expert". I don't know, why this 
always happens to me, after collecting all the Z-System files 
and distributing some Z-System programs, everybody expected 
me to be a Z-guru. In order to read some news from comp.os.cpm 
I got an account in a publicly accessible UNIX machine. To be 
able to at least do the routine stuff, I had to read lots o ' man 
pages. In the middle of getting less dumb, I got the o fer to 

The Computer Journal / #70 


woric as a UNIX teacher! I promise, I hadn't intended to do 
anything in that direction, but it seems, these things just 
"happen" to me! 

So I guess, being an idiot is not such a big problem, as long as 
everybody else is a) either equipped with less knowledge than 
you, b) believes you know more than they do, c) is ignorant of 
the right time to say yes. 

In any case, I can now call myself an expert idiot. 

Thanks for the background info and now on to this issue 's 
regular fair from Europe. BDK. 

Sweet End of Sugar for Computers (More about 

Well, last time I gave you the insights into AMSTRAD's CP/ 
M machines, the software and the sales development. You got 
your first impression of "European feel" in the computer world. 

AMSTRAD DPBs and Typical System Commands Beyond the 

The AMSTRAD CP/M world had always been split into two 
parts: CP/M 2.2 and CP/M Plus. Not only was there total 
incompatibility of terminal commands, but different disk for- 
mats and tools. 

In the traditional CP/M 2.2 world there was SETUP tools, and 
a lot of things could be performed with a batch file via SUB- 
MIT, which influenced CP/M Plus. In CP/M 2.2 there is only 
the so-called I/O-Byte that coimected the devices to the oper- 
ating system calls. In CP/M Plus a generic AUX device is 
accessible, independent of any settings. 

The AMSTRAD CP/M 2.2 SETUP aUows you to modify the 
keyboard settings, such as the arrow keys in Normal, Shift, and 
Control level. This required quite some concentration and lots 
of skill, since small errors could affect screen colors or 
windowing.The CPC supports true windowing by use of one of 
the most popular characters: CTRL-Z! So, whenever you acci- 
dentally ran a program set up for Televideo or ADM3A char- 
acteristics, you ended up in a screen size of 0, since those 
terminals use CTRL-Z as the CLEARSCREEN sequence, fol- 
lowed by a Null-Byte. 

Today, a convenient adaptation of the CP/M Plus SETKEYS 
has been written for CP/M 2.2 by one of the most skilled 
authors in our club, Robert Steindl. 

The greater handicap is the AMSTRAD CP/M 2.2 BIOS 
(AMSDOS) itself, which supports only single-sided disk for- 
mats with 40 tracks, although it includes a (nowadays unused) 
standard format, the SS40 IBM format with 8 sectors (old CP/ 
M86 format). Mind you, there is no such thing as a 3" disk on 
an IBM CP/M86 machine! Of course, some companies offered 
programs to manipulate the Disk Parameter Block (DPB) in 

order to handle alien disk formats, but then they were not 
widely known and were available only in certain areas. 

Again, CP/M Plus put an end to most of that. The whole Disk 
Parameter Block resides in one line inside the CP/M Plus 
memory, making it easy to patch and modify even from the 
command line, provided one has the proper tools (PK.COM). 
If a small patch was made to the system file, the .EMS file on 
the boot disk, even two-sided formats could be used. By using 
the proper system function, GETDPB, any altered CP/M Plus 
system could deliver the address of it's DPB, and so any 
program could search for it and modify it. Unfortunately, most 
PCW programmers are unaware of these standards and keep on 
using fixed addresses, hardcoded inside their programs. Those 
will have to be rewritten in parts to run on the CPC's CP/M 

An example is the program DU+49 (the programmers weren't 
even aware of the existing DU-series programs), which can 
cause tremendous heartache, even to owners of a PCW, if they 
have any modifications or add-ons in their machine (or at- 
tached to it). As a matter of fact, we have a certain circle of 
programmers busy repairing the sloppy output of others. 

There is a certain goodie buried in the Disk Parameter Block 
of the AMSTRAD CP/M Plus - the so-called Freeze-Flag. The 
name signals it's function: if set (FF Hex), the DPB is "frozen" 
and cannot automatically adjust itself to the inserted new disk's 
format (especially on the PCW, this Auto-Login information 
can be a serious trap). That is the only way that an alien disk 
format can be used properly. Otherwise, every warm boot or 
disk reset would cause a reset of the DPB information to the 
values stored in the BIOS, and sometimes this happened by 
accident when CP/M Plus read some code similar to it's log- 
information at the beginning of a disk. 

The CPC's CP/M Plus differs from the PCW series quite a bit, 
although the typical functions of the BIOS are the same and 
properly implemented by a BIOS call (BDOS 50, 1 think) with 
an offset parameter to specify which BIOS function was called. 
This is very important when a disk formatting program is used 
on both computers. The average PCW programmer tends to use 
absolute addresses and thus causes a lot of trouble. Just imag- 
ine: a two-sided disk is specified by 01 (Hex) on the CPCs, 
where on the PCWs the value is 81 (Hex). Although this just 
means using the high bit, many disk tools fail to serve both 
computer types, although they are made by the same company. 

With these thoughts, I'd like to conclude our first excursion 
into the AMSTRAD world (for most of you). If you find this 
subject interesting, I could try to shed more light on other 
aspects as well, so feel free to write letters to TCJ or to me 
directly. You may reach me through either CompuServe 
100024,1545 or via GEnie: would be 
the INTERNET version of my address there. GEnie users will 
probably have detected me by now as a contributing sysop for 
CP/M Roundtable there. 


The Computer Journal / #70 

Many people from the US can hardly imagine how differently 
CP/M developed in the US and in Germany. This is why 1 want 
to tell a little about the backgrounds as I experienced them. 

In 1982 CP/M had made its way into German offices. High- 
priced computers and high-priced software lived a happy, 
reliable (and virusfree!) existence in the holy places of indus- 
try. Before 1984, it was hard to get low-priced, quality equip- 
ment for private use. So, no wonder an active scene started to 
develop, following the spirit of the HEATH radio amateurs in 
the sense of building, soldering, and even developing hardware 
and software. 

Of course, there were the industiy standards: Apple II, Radio 
Shack's (Tandy) TRS-80, EPSON QXIO, Wavemate BuUet, 
Bondwell 12/14, and Kaypro II, IV, and 10. Many others one 
only knew by name, since they either never made it out of the 
offices, or they were not in use at all in Europe. This fact shows 
up clearly when you get a format converter/reader hke 22DISK 
(DOS, sorry) that contains lots and lots of formats that people 
in Europe never heard of On the other hand, most of the 
common European formats are missing and have to be defmed 
by hand. 

A good example is the GENIE lis, a German post-development 
of existing hardware, compatible to the TRS-80 and disk- 
compatible to the COLOR GENIE. The operating system 
"NEWDOS 80" was so-so, but "G-DOS", the German hom*rew 
operating system, had exciting extra features. That gave me a 
hard time when I tried to convince people of the superiority of 
Z-System. Unfortimately, I don't remember exactly what those 
features were. One good thing was that the GENIE lis uses the 
ECB-bus concept, giving it access to a variety of add-ons, like 
EPROM-cards and the hke. 

This brings us to the main big thing in Europe: single-board 
computers (sometimes called EMUFs) and ECB-bus type com- 
puters. Of course, there were always some that made up their 
own "standard", like the NDR-Mikrocomputer. Notice the "k" 
in micro. Zeds tsherman! But what is this ECB-bus like? The 
concept is based on a back plane with several sockets of 96 
contacts each, that connects all I/O, clock, and supply wiring 
along its "bus". The 96 pins are divided into three rows of 32, 
named a, b, c. Most of the time, b is not used, thus leaving a 
so-called a-c wiring. The male connector slides quite well over 
the female on the back plane by means of a square edge and 
also establishes a very good mechanical connection. 

This system is easy, professional, and less hay-wire than the 
IBM slot system still used in today's 486 clones. Maybe that is 
the reason why in 8-bit environments the European industry 
still makes extensive use of the ECB-bus system. Other bus 
systems, like the SlOO bus, never really made it in Europe. 

One of the developers for today's industrial ECB applications 
is Tilmaim Reh, of whom we shall hear again later on. 

The idea behind it all was to be able to use all sorts of different 

hardware on a given system. An ECB-bus EPROM-program- 
ming card could be used on every ECB-bus machine, given the 
correct I/O-address and software adaptations. Soon there were 
SASI cards, which opened doors to hard-disk and backup 
media, as well as IDE interfaces, disk controllers, and even 
complete terminal cards, suited for the Hercules monitor and 
IBM-type keyboard. But then, of course, there was a long way 
to go before that goal was reached. One of the most widespread 
home systems was KONFTEC's PROF-80, widely featured in 
the c't magazine at that time. They, too, offered variants of that 
design and add-on cards, like the PROMMER-80, an effective 
hardware tool to produce all sorts of BIOS variants. Some 
people added an OMTI-controller and got together to write a 
new BIOS to integrate a hard disk. Uwe Herzceg, one of my 
early Z-contacts, finally succeeded. It was one of those great 
moments when he had a full-blown system and had managed 
to implement my favorite disk format (CPC VORTEX 704K) 
into his BIOS! 

Another strong line was pushed even by television, the NDR 
Klein Computer. There were unfortunately at least two differ- 
ent bus types. One of them was the ECB bus, but the other one 
was good for that machine alone. There were a lot of efforts to 
keep the system design "open", so it takes quite some work to 
keep track of all the "native" formats. I have about five NDR 
customers, each using a different format. Great. I think, this 
shows best what the European CP/M situation was like. 

Few companies took the pain to really do things properly, as 
KONTRON and a few others did. They implemented a oro- 
gressive mainboard concept in a 19" rack with an optional hard 
disk controller board. The floppies were already in 5.25" for- 
mat, and the terminal could be integrated with the machine. 
Such combinations with high-resolution graphics were widely 
used in medical environments for ultrasonic and cardiographic 
applications. Every now and then, one of those machines 
appears from nowhere. Most often it is a PSION 80, the most 
advanced model at that time, but using a single-deiisitj' disk 
format, which is not supported by 22DISK on the IBM clones. 
The BIOS was well written, aind boot -up could be uiterrupted 
to jump into a system monitor capable of assembly Language 
instructions. The system could be oonfigiu-ed to boot cff floppy 
or the hard disk. 

Needless to say, they used their own terminal codes 

So, to view the whole, you can see that the European CPI^ ' 
scene started out with complete machines, most of them with 
an integrated terminal and specialized for certain tasks, net i ^ 
many of them having standard CP/M operation in mind. This 
created the situation I (among others) face today: first to make 
the real CP/M environment accessible to the later owners o*" 
those industrial dropout beasts, then bring Z-system or the like 
to them for their own benefit. 

The weirdest situation, though, was in Eastern Germany (Wall 
scenario). There was only one ompany (Robotron) nally 
capable of building usable m.^chines (f; state said ot i is 

The Computer Journal / #70 


enough) and so they built hardware (they copied and stole some 
of the AMSTRAD techniques and a few others) and they 
cloned software. They made rewrites of WordStar (TP.COM), 
dBASE II (REDABAS.COM) and others. When the Wall fell, 
the company broke up, and the programs became orphaned. If 
you are looking for a database program, give RED ABAS a try. 
You'd have to give it a little hack to accept .CMD files as 
program input, and sometimes the MODIFY COMMAND 
does not work properly, but the rest is fairly acceptable. I 
recommend using ZDE anyway, since dBASE, too, has a bug 
in it's editor and always trails garbage at the end of an edited 
program file (probably no CTRL-Z). 

Naturally, as soon as I got my first contacts, I tried to imple- 
ment NZ-COM on the CPA (CP/M clone) and the SCP (the 
other CP/M clone). The termcap turned out to be a sUght 
disaster at first. The cursor sequence looked as if it used only 
ESC. After my first fright, I used a debugger to look into 
TP.COM (WS-clone). There I found what I had been hunting 
for: ESC was followed by HEX 80, which naturally was trapped 
by the output mask of CP/M (HEX 7F). After that, it didn't take 
long, and NZ-COM could be sold for the ROBOTRON ma- 
chines. The disk format is quite easy and uses a logical layout. 
There are foiu- different formats that I know, the most used 
being a 780K format (DSDD or "Quad-Density", a term some- 
bo(fy had made up but really doesn't exist). 

This whole mixture of CP/M machines could only be dealt with 
by a machine with a standard controller and a very good 
program to handle all the formats. Of course I hear you say 
"22DISK on my IBM PC!". But that is not what it is all about. 
I mean a CP/M machine, able to do real mean tricks in sector 
translation, side access, skews, mixed or even high-density or 
the like. I kept looking. I glanced at the PROF 80 of Uwe 
Heizceg and felt pretty poor with my AMSTRAD CPC, even 
though I could read some formats. 

Then Uwe gave my name to a guy who was looking for an 
assembler for the work on a new processor, the Z280. So this 
guy, Tilmann Reh, called me up. After some telephone calls, 
we were in good contact, and the more I learned about his 
plans, the more interested I got. When he aimounced his new 
single-board ECB-bus computer CPU280 and told me about 
the format manager, I packed my stuff and traveled to the next 
meeting he held in his house. Imagine, a living CP/M machine 
constructor and supporter! I immediately ordered my "ma- 
chine". So, after some weeks, I got a parcel containing wonder- 
ful shiny little capacitors, resistors, carefully packed chips, 
most of them in conventional form, some in new square hous- 
ings, one of them being the legendary Z280. Tilmann had 
never before in his life tended to swear and curse, but talking 
about his experience with the sloppy development of the Z280 
and all it's mask bugs, he had to add a few words to his 
vocabulary. After two years, he still has problems to say the 
name ZILOG in a cool, unaffected manner. 

Anyway, after four hours of concentrated soldering, and three 
hours of setting up my AMPEX terminal, I got the thing going! 

It worked like a charm, but soon, after seeing an increase in the 
need for high-density drives, I had to exchange them. Nowa- 
days, I am still using four drives (I could use 8 "-drives, but I 
don't need to), two 5.25" HD drives and a 3.5" HD drive, plus 
an optional 3" Hitachi drive, that allows me to work with 
AMSTRAD disks as well. The 3" drive is not needed con- 
stantly, so it's connected externally. That was the time when 
many ECB bus machines were torn apart, leaving only the 
drives and the power supply. Some (the PROF80 users) had an 
intelligent terminal card, the GRIP card, that they also left in 
there, and some even had EPROMers and static, battery-backed 

As the CPU280 community grew, Tilmann was encouraged to 
offer add-ons, aside from his software improvements and BIOS 
updates. So, not long after our start-up, the IDE controller card 
was presented to us. This was the final thing I had been waiting 
for: 80 MB right at hand from CP/M! I must say, whenever one 
of my two IBM PC clones let me down, I looked at the CPU280 
with a grin and said: "good to have you, I don't really need the 
bastards, ey?" Well, it is partly true. One of them became the 
home of the reissue of ZNODE #5 1 , the only CP/M and ZCPR 
bulletin board and file source in Germany accessible for free, 
no download charges, cross-system discussions, local program- 
mers forum, and of course, all that Z. 

Let's hope I come up with a good idea for my next article. My 
little baby, YANNICK, is taking lots of daddy's time and 

Regards and cu 

Helmut Jungkunz 

(P.S: I'd be glad to receive your comments on my articles, best 
through e-mail, since this creates a computer file that can be 
passed to others.) 



Classified ads in TCJ 

get results, FAST! 

Need to sell that special older 

system - TRY TCJ. 

World Wide Coverage 

with Readers interested in what 

YOU have to sell. 

Provide a support service, 

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The best deal in magzines, 

TCJ Classified 

it works! 



The Computer Journal / #70 

TCJ Center Fold 

special Feature 

All Users 

Jupiter ACE 

Some time back I had mentioned wanting to use a Jupiter Ace. 
This is the ZX81 variation that ran Forth from ROM. I saw 
sssKxA versions when they were produced, but considered their 
price a iHt steep for me. The unit comes with a very good book 
by Steven Vidcers Ph.D. that gives you all the Forth informa- 
tioB needed to write programs on the ACE. The bode explains 
tlat ACE stands for Automatic Computing Engine. The back 
cover states that: "After Studying mathematics for eight years, 
fiist at King's College, Cambridge and then at Leeds Univer- 
se where he gained a PhD in algebra, Steven Vickers turned 
to cooqwter programming and played a large part in develop- 
'\B% the Sinclair ZX81 and ZX Spectrum." 

"In I9m he read The Hitchhiker's Guide to the Galaxy and, 
fealiang that its high content of factual errors made it umeli- 
^e for {H'actical use, decided to rewrite it. The result was what 
is by now probably the best-selling computer manual ever, for 
tte ZX81. He also wrote the manual for the ZX Spectrum." 

"In 1982 he and Richard Altwasser set up Jupiter Cantab Ltd 
and designed the Jupiter Ace." That sounds like great creden- 
tials 1o me. There is also a ch^ter in the back of the book that 
gives a hardware example of using the ACE to control stop 
Vt^Bis. The pinout of the expansion interface is given, plus 
iniScafing that it is compatible with the ZX81. 

I recdved a bare board and ROM from Etonald A. Gaubatz. We 
have been e-mailing and talking about getting the source code 
its tiie RC^'s. Donald became acquainted with the Jupiter 
Ace while he was doing a Ph.D. at Cambridge University 
Con^iiter Laboratory. 

In a l^ter to me, Donald states "Jupiter Cantab Ltd. stq>ped 
bigness (qwrations in late 1983 and the product was taken 
ovw by a local computer retailer. I bought a Jupiter ACE, 
games, ttc., fat my children to play with, and, subsequently 
acqimed some hardware and firmware items when the retailer 
also storied selling the product. I purchased these things with 
the goal of modifying the design, specifically with regards to 
the cassette tape interface." 

He continues, "The firmware disks I have are 8" hard-sectored, 
as used by the ZILOG MCZ Development System. I also 
acquiied a ZILOG MCZ-1 (again, repatriated from England), 
bat it does not seem to work. Presumably, these disks contain 
the source for the ACE ROMs." I am aware that several of 

rCTs readers have these old development systems, possibly 
one still working, and we need to see if we can get one to 
Donald in Massachusetts ( use ). 

As you review the design of the ACE you can see why it makes 
a good design for training. The design is sin^jle, without any 
special chips. The keyboard could be built using 40 simple 
push buttons, although I feel that a serial port might be more 
appropriate for getting data into and out of the machine. I dare 
say most user would have all the parts sitting in their junk 
boxes waiting for this design. 

To help understand the design you need to check out ch^ter 
25 and 26 of the book. The RAM and ROM addresses are 
barely decoded and as such appear in many places in the 
memory map. In the early days of micros, that was a very 
common design, after all few could afford lots of memory. The 
prd)lems came later as people tried to expand the memory. 
Basically the address decode section needs to be redotie. As the 
design now stands, address lines 10 and 1 1 are not decoded! 
That means all devices get decoded four times in the map. 

There are a few interesting chips that need to be pointed out to 
the novice designer. The LS166 shift register provides the 
means of shifting the video bits into the video stream. Charac- 
ters are changed from ASCII values to bit maiq)ed rq)resenta- 
tions and stored in the video RAM. The bit m^ped values are 
then read from RAM in parallel into the sh^ register that 
converts the data serially into the video stream. 

The LS393 are ripple counters that are used as clock dividers. 
That means that these devices control the timing of when 
things hai^n in the machine. We start out with a 6.5 Mhz 
clock and divide by a half. That gives the 3.25 Mhz clock to 
a transistor that inverts the signal to drive the Z80 CPU. It is 
a very simple way of getting a number of signals to drive the 
system and maintain proper relationships. If something is to 
take place every four clock cycles, dividing the clock by 4 will 
give a pulse at just the right time. 

Since the frequency of TV sets in Europe is different than in 
the USA, other clock frequeiKies where used. The European 
version of the Jupiter Ace is shown on page 28. 

I hope you understand the simplistic nature of this design md 
see how a modem day version could be constructed. 

The Computer Journal / #70 

Center Fold Section 





Center Fold Section 

The Computer Journal / #70 

The Computer Journal / #70 

Center Fold Section 








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Center Fold Section 

The Computer Journal / #70 

PC/XT Corner 

Guest: V. Henry Vinerts 

Regular Feature 

Intermediate Users 

A Stepper Motor Project 

While at The Embedded Systems Conference, I found a copy 
of Frank Sergeants system running and stepping. That is to say 
a real life size version of the article. The booth was Silicon 
Valley Forth Interest Groups and Dr. Ting and V. Henry 
Vinerts were maning it I talked to Dr. Ting for a minute, then 
settled in for a who,''what, and how of Frank's design. For 
those who have seen me in person, I have rightfully earned a 
reputation for arm twisting in hopes of getting an article. Well 
Henry's arm must still be intact since he sent me these 
drawings and explanations. BDK. 

October 10, 1994 
Dear Bill, 

Just received your note on GEnie, and this writing comes at 
your suggestion, with a copy to Frank Sergeant. As I said 
before, I was glad to see you stop by the Forth booth at the 
Embedded Systems Conference in Santa Clara, a few weeks 
ago; and thanks for the request for a blurb about my stepper- 
motor demos. 

There were two: the Etch-a-Sketch and the Peanuts Gang. The 
first featured two stepper motors connected with rubber bands 
to a medium-sized Etch-a-Sketch screen from the local toy 
store; the second- Lucy, Charlie and Snoopy doing dances on 
turntables moimted on stepper motors. The controls were by a 
PC laptop through the parallel port with software provided by 
Frank Sergeant's Pygmy Forth. So far we still haven't drawn 
the perfect circle on the Etch-a-Sketch, nor multi-tasked the 
dance routines with music, but 1 am working on it. Some 
pictures are still in the camera, but, 1 think, my sketches from 
the project may be of more interest to your readers. (I am 
sending the basic controller sketch by U.S. mail.) 

The idea for the Etch-a-Sketch came to me some time ago, but 
I probably wouldn't have gotten very far without Frank's 
recent article in the PC/XT Comer. The main message I want 
to convey here is that 1 feel good about actually having built 
something that combines elementary hardware and software, 
that I _almost_ understand and can control with my own will 
(and that is unusual in this hi-tech world of ours). It means 
much more to me to do something simple well, than to dabble 
in and fiunble with complex systems whose inner makings are 
guarded by the self-elected few who may have created the 
complexity in the first place. 

Yet, a task well done looks simple, a problem once solved, is 
easy. To get to this point with the steppers, I've had to learn 
quite a bit. It would take too long to go over all of that here, 
but let me list a few thoughts and a few questions — they may 
germinate some material that belongs to the "raison d'etre" of 

There must be more variations of stepper motors than there are 
dialects of Forth. The number of wires, steps, voltages — all can 
vary, but the first thing is to recognize whether a stepper is 
bipolar or unipolar (bifilar), that is, whether it needs a switch- 
ing power supply or a regular unipolar power supply. (There 
are enough mystery words right here in one sentence. How 
about "EFSS" region of a stepper, that Charlie has to watch in 
order to stay in synch with Lucie? You see what 1 mean by 
getting to the inner secrets of the state of the art? If we need to 
search fiuther to get the job done, there are books and more 
books.) My first stepper was bipolar and would not work with 
the scheme that Frank described. The present steppers (at 
$3 .50 each, from a surplus store) are Airpax specials, and I was 
able to get a nice catalog-"Stepper Motor Handbook" -from 
Airpax in Cheshire, CT, that helped a lot. So, get to know your 

Next, whatever you wish to turn, will require a little engineer- 
ing. Engineering means numbers. "Let me make some num- 
bers" means that an engineer wants to turn over the napkin or 
the envelope, doodle, scribble and calculate a bit and come up 
with a prediction of whether something will or will not work 
as Mother Nature intends it to be. Of course, the decimal point 
must be in the right place, though. Now, in my case, I started 
out without making any numbers and wound up "cooking" 
some chips. I still don't know what defines a power transistor, 
but the TIPl 20 Da. . In; tons from Radio Shack can handle the 
1 amp at 5 or more volts gsing through my steppers. 

The trouble is that all that juice still wouldn't work the Etch- 
a-Sketch. This is where I remembered about the "numbers". 
Turned out that it took 32 U. S. quarters in a bag tied to a string 
that hung from a 1 1 1/16" dia. homemade pulley (from closet- 
pole sockets) to turn one shaft of the Etch-a-Sketch. The 
kitchen scale told me that 40 quarters weigh a half-a-pound 
(that means you can buy a pound of quarters for $20), so the 
torque needed to work the sketch worked out to be about 5.44 
ounce-inches. The stepper motor did not like that at hi , her 
speeds, so I had to equip it with a small pulley — about 1116" 

The Computer Journal / #70 


dia. screen door roller— in order to get a workwise trans- 
mission. For right now, various combinations of rubber 
bands have been tried, but they all create errors in 
motion reversal from slack to stretch. It is pretty hard to 
program a perfect circle, but I must say that my 12-sided 
figure program produces the same inaccurate tracings 
with amazingly reliable repeatability. (I am shopping for 
a set of plastic sprockets and chains, but my interest 
dwindles. Control is possible, corrections can be made 
with software. Q.E.D.) 

Last, but not least, as I work on adding music to the dancers, 
I find that my Toshiba TIOOOSE laptop behaves differently 
than my XT or AT as far as the 8253 chip features are 
concerned. I cannot get the sound to continue. Is there a 
different chip on the Toshiba? Also, if there are any unhappy 
Toshiba TIOOOSE owners out there, three of us here in the 
Silicon Valley Forth Interest Group have developed an inex- 
pensive battery pack renovation procedure. Would it be worth 
writing about? 

So much for now. Sincerely, V.Heiuy Vinerts, 36139 Chelsea 
Drive, Newark, CA 94560. 

Thanks Henry! I especially like the way you found out how 
much energy was needed to turn the wheels, very novel idea! 

Yes, it is important to sometimes crunch those numbers I must 
admit to sometimes being lazy and not doing the math, but then 
experience can sometimes give us rules of thumb that work Just 
as well. I usually like to get my steppers from working ma- 
chines, so I can compare and see what circuits and pulley sizes 
were used. This gives me an idea about where to start, and if 
I need more force than they did - change wheel sizes accord- 

You really didn 't explain about your major problem, which I 
hope you 've solved. When doing simple projects like this (well 
simple results -but complex research work) it is hard to Justify 
spending money on real notched belts. As you explained to me, 
what is needed is real drive belts that can be tightened and 
have enough "traction" that slippage goes away. Frank's 
desire of an XY table has got him into considering real worm 
drives in which the slippage is minimal The slippage we speak 
of, is the loss of movement that often occurs when you change 

Slippage is always a problem, but very expensive drive mecha- 
nisms that have small amounts of slip, explain the cost that 
prohibits Frank from buying them. The best are worm gears 
and mating collars that have been machined such that the gap 
between parts amounts to a good film of oil. Less accurate but 
with more acceptable slip, are cogged or toothed belts Slip- 

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The Computer Journal / #70 

page occurs herefrom stretching in the belts, loose belts that 
allow the cogs to slide a bit out of the tooth of the gear. 
Backlash describes the slippage (and caused Henry his big 
problem) when directional changes may waste a full step or 
more. If you have a little slip in one direction, changing 
direction will normally produce twice that amount of slip. 

There are some trick one can use to mitigate slippage. Adding 
drag or friction so that the drive mechanism is under a con- 
stant pressure often helps prevent overshooting. Too much 
drag can however cause stretching of the belt as the force 
needed to get moving is greater. Spring loaded idlers (often 
seen on car fan belts) can cut slippage in both directions by 
adjusting the tension automatically as the belt moves This 

adjusting keeps the "slop " to a minimum without adding to the 
drag, even though the results is about the same or better - a 
constant tension on the belt in both directions. 

I do not know of a beginners level engineering book that would 
not require 4 years of college to understand that might help 
our readers master the mechanical side of steppers. If you 
Henry, or any reader know of one, please let me know. Just 
remember that plenty of inventions have been created by non- 
professionals using tools as simple as a bag of coins. 

Thanks Henry for your great project Bill Kibler 

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The Computer Journal / #70 


32-Bit Systems 

All Readers 

CO*ROMs and News 

Real Computing 

By Rick Rodman 

Recordable CD-ROM, aka CD-R 

Let's talk cents per media megabyte. 
Hard drives are going for around 80 
cents per megabyte, down to about 50 
cents for high-capacity drives. Syquest 
and Bernoulli are around the same price. 
Floppy diskettes are about 30 cents per 
megabyte. Optical (WORM or MO) 
cartridges can be as low as 10 cents per 
megabyte. Tape is around 8 cents per 

Recordable CD-ROM media sells for 2 
to 3 cents per megabyte. 

Not only is CD-R cheap, read-only drives 
are plentiful and cheap. By contrast, 
optical and tape drives are expensive 
and involve device drivers and/or driver 
programs. A more important factor is 
the ISO-9660 standard: You can write 
a CD on a PC, and read it on a Mac, a 
Sun, a VAX, or anything else. 

There are drawbacks - you have to write 
a whole disk at a time, the capacity is 
small for some applications, and CD-R 
disks are fragile, with media life uncer- 
tain - but the cost and standardization 
advantages are so overwhelming that we 
can expect CD-R technology to become 
the most widespread data-publishing 
method used for the next ten years. 

Okay, you've read all that before, and 
this is TCJ. so let's stop eating hush 
puppies and get on to the flounder. 

Writing your own CDs is easy to do. 
Finding enough data to fill a CD may be 
a Uttle harder. To write a CD, you need 
a &st computer with a fast, large, hard 
drive. A Pentium PC with a 1GB SCSI 
drive is a good choice. Second, you should 
probably try to have a dedicated SCSI 

adapter for the writer. No scrimping here 
- 1 suggest an Adaptec 1540 or 1740 (for 
EISA machines). 

Then you need a writer. These drives all 
have very differentcharacteristics. Some 
are faster, some are smaller, some are 
che^)er. The new Yamaha 4x speed drive 
is the fastest and the smallest, but it 
costs about $5,000 and, being faster, will 
require a very fast machine to write to it. 
Mine is a Ricoh RS-9200, which is a 
single-speed drive, small, and inexpen- 
sive - about $2,500 and falling. 

Of course, you need software. And there 
are lots of choices. The software that 
comes bundled with the drive may or 
may not be the best for you. There are 
lots of decisions to make - Do you want 
Orange Book? Do you want multisession? 
Do you want CD-DA? Do you want 
Rock Ridge? For my purposes, I only 
wanted the basic ISO-%60, to write plain 
single-session CD-ROMs, for backup and 
for data. 

The software that was bimdled with my 
drive is Incat Systems' Easy-CD-Pro. 
This is a Windows package, with a slick 
drag-and-drop graphical interface, but- 
tons to click, and a nice manual. Very 
easy to use - just drag a directory and 
drq) it on a "virtual CD". Then write 
when you're finished. Drag, drop - and 
wait. Drag, drop - and wait. 

For some people, this may be fine. For 
me, it was tedious. Each time you drop 
a directory, you have to wait several 
minutes before dropping another one. 
Graphical interfaces become aimoying 
when you're looking at homglasses for 
long periods of time. Building the "vir- 
tual CD" can take hours - and it has to 
be done every time you write a CD. 

The most annoying part of Windows- 
type graphical programs is their invis- 
ibility. You can never tell what's going 
on. Your choices are always severely 
limited, so there's never any way to ask 
anything. For example, several times I 
got a message "Servo error" with a single 
"Ok" button. What does this mean? What 
should I do about it? Not only is there 
nowhere to look, but there's no option at 
all - just grunt and click "Ok". 

There's an old saying that free advice is 
worth every permy you paid for it, and I 
feel the same way about some free soft- 
ware. I'd rather not get any software 
with my drive, and use the money saved 
by a lower price to go buy software I 
want. In my case, the software I bought 
was Corel SCSI version 2, 

Corel SCSI has a simple program called 
CDCOPY that makes writing a CD as 
simple as using XCOPY. They also have 
an XCOMP program that lets you verify 
an entire CD, producing a log file of 
errors. Better yet, CDCOPY lets you use 
a "CFG" file to write a list of directories 
to a CD. Best of all, they let you put 
comments in the file so you can keep it 
as a documented "soiu^ce listing" of the 
CD backup operation! 

I about fell out of my chair when I read 
that you could add comments. This is a 
mark of a good programmer somewhere 
at Corel. If you want to tell a real pro- 
grammer from a rookie, look at their 
comments - real programmers write com- 
ments nearly every line; rookie program- 
mers go without comments for pages, 
maybe even whole files. 

As an aside, I had to chuckle when I 
read in Mr. Anderson's column that 
someone thought of 100 bytes as a large 


The Computer Journal / #70 

program. Program size is usually mea- 
sured in soiu'ce lines, and the common 
criterion is that less than 10,000 lines or 
less is a small program, 10,000-99,999 a 
medium size program, and 100,000 and 
up a large program. Assembly-language 
programs seldom go into the large range. 
As for myself, I am on only the second 
large program in my career, and both 
have been in C. 

Some folks will tell you that drive speed 
is the main criterion for selecting a CD 
writer. I'm here to tell you, it isn't. 
Phihps says that their CDD-52 1 can write 
a CD in half an hour, whereas the Ricoh 
takes a whole hour. By this logic, the 
Yamaha could write a CD in fifteen 
minutes. Don 't believe it! There is so 
much overhead in writing a CD that 
writer speed is almost irrelevant. You 
can count on writing a CD taking at 
least two hours, and of course you have 
to verify the CD, which actually takes 
even longer. With Corel SCSI, I can do 
the verify in a double-speed read-only 
drive. You can figure on ^x)ut four hours 
total to do a CD. The Yamaha might get 
it down to three, but I wouldn't count on 

Think about it., in 1981, companies paid 
$5,000 for XTs which are being tossed 
out today. For $5,000 you could set up a 
PC for them with a 2-gig SCSI hard 
drive and a CD writer. You supply some 
batch files that xcopy their data from 
their fileserver, which they would run 
on Friday evening. As a backup system, 
it's even cheaper than tape, since they 
wouldn't need an ofiF-site tape drive to 
read backups in the event of fire -just a 
PC with a CD-ROM drive. And who 
said they could only use it for backups? 
Lode at all of the other possibiUties it'd 
open up. 

A mammoth change is taking place in 
the computer world before your eyes. If 
you can't profit from it, at least be ready 
for it. 


I don't like the Phihps because, although 
it's only a little more expensive than the 
Ricoh, it's a lot more expansive. It's as 
large as an old AT, with only a few little 

lights on its big, blank, tan fece. 

This is the way computers are today - 
big, blank tan boxes made of cheap- 
looking plastic. When will these guys 
ever learn? Some PC makers nowadays 
are starting to put httle "louvres" or subtle 
indentations on their boxes, and some 
are coming out with all-black cabinets 
instead of ubiquitous tan, but these are 
only very minor changes in a packaging 
trend which can only be characterized as 
dull, duller, dullest. 

Nominees for worst cabinets of all time 
are: Dell, for its plastic PC chassis which 
has to be warped and twisted to line up 
the screws, which strip out readily; 
Compaq, for its Systempro chassis, 
which, once opened, is almost impos- 
sible to close without a hammer; and 
Zenith, for its PC chassis which, though 
metal, still require bending and twisting 
to get the screws on its side (echh!) to 
line up. Nominations are still open, of 
course. Let us share your horror stories. 

Best computer cabinet of all time? No 
contest here. Undisputed wiimer - the 
Imsai 8080. A pleasure to look upon, 
with all of its LEDs and switches - a 
cabinet that says. Here is a real com- 

Dull tan boxes just show the infancy of 
con^uter technology. In the more ma- 
ture world of stereos, where interfeces 
are standardized and controls mostly 
agreed upon, cabinets have been an area 
of real design iimovation for at least 
thirty years. Set an expensive PC next to 
a cheap stereo. See what I mean? 

Here's an idea for an entrepreneur out 
there: Make a display box which fits in 
a drive bay of a PC. My plan was to put 
a circuit board on a 3.5-to-5 drive adap- 
tor. This circuit board would be con- 
nected by a ribbon cable to a board 
plugged into the backplane. The front 
would be smoke plexiglas, behind which 
was a dazzling array of LEDs in various 
colors and of various types. I'd like an 
array of small LEDs showing the ad- 
dress bus, latched by certain bus condi- 
tions. Some LEDs would be under pro- 
gram control. This thing would not only 
be neat to look at, but would actually be 

useful for program dd)ugging. And it 
should be cheap and easy to build, too. 


"Enclosed is the documented vector us- 
age for the Xerox 820-11," writes Duane 
Ruck in response to my queries in #68 
regarding the Xerox 820. "It looks like 
the first 8 should be just the thing for 
your networking code." Enclosed were 
excerpts of a monitor listing showing 
interrupt vectors. The listings also show 
the keyboard FIFO and the time-of-day 
locations. Thanks for the excellent in- 

I'd also like to thank Mr. Kaypro, Chuck 
Stafford, for his quality documentation 
on the Kaypro 10. This is one of the 
main reasons that older machines have 
kept their value: Excellent documenta- 
tion is available. By contrast, PC makers 
guard technical information as though it 
were family jewels. 

I have little to report myself. In trying to 
use Eco-C on the Z-80, I've had lots of 
problems. Jay Sage has provided me a 
copy of Hi-Tech C, which looks pretty 
good. I'll end up either using this or 
using EDS C 1.6. I've been doing a lot 
of compiling on a Pentium PC using 
Z80MU, rather than on the Z-80 itself. 
According to Z80MU, my P90 is emu- 
lating a Z-80 running at 52 MHz! 

Next time 

We get back to the Linux scene and 
review happenings there. Then it's on to 
TCP/IP land for a discussion of routing, 
network addresses, and subnets. Time 
and space permitting, from there it's 
networking, NFS, CD-ROM sharing, and 
other neat stuff. Until then: Compute 
happy. Compute hard. Compute proud. 

Where to call or write 

Real Computing BBS or Fax: +1 703 
330 9049, E-mail: 
Mail: 8329 Ivy Glen Court, Manassas 
VA 22110 

Corel SCSI version 2, $99 at a store near 
you. Corel Corporation, 1600 Car ing 
Ave., Ottawa, Ontario KIZ 8R7 Ca ada 

The Computer Journal / #70 


Regular Feature 

68xx/68xxx Support 

6609 Assembly & Flex 

Small System Support 

By Ronald W. Anderson 

A Correction (or a better way) 

Two columns ago, I presented a short utility to set a printer to 
a different print mode, specifically my Citizen to the 12 cpi 
mode. I showed a really dimib C program that output a char- 
acter at a time, and then realized that I could output the 
commands as a string, but drew a blank on outputting a null 
(ASCII 0) in the middle of a string since C uses the null as a 
string terminator. I wrote my own output routine (true, it was 
only one line and was a way to get the job done). It has since 
occurred to me that I could have used the "escape character" 
\0 in my string and C's fputs() function would handle that just 
fine. I just tested that out, and it worked. I'll import the C 
source file here: 

// set citizen to draft 1 2 pitch hi density 
#include <stdio.h> 

FILE 'printer; 

charcodesQ = {0x12,ESC,0x4d,ESC,0x78,'\O',ESC,0x7e,0x42,0xO1}; 

void main() 


printer = fopen('lptr,"w"); 

This version is 9053 bytes long, actually a few bytes longer 
than my previous effort, but it is at least aesthetically more 
pleasing to use a feature of C that lets me use one of the 
standard library functions to advantage. 

I think someone ought to write a book "C for Dummies" to go 
along with the standard "DOS for Dummies". I've been using 
a comfortable subset of C for quite a while, but recently I 
decided to at least begin to explore some of the more "ad- 
vanced" features. The language PL/9 that I have been using for 
so long to program 6809 systems is excellent as far as it goes, 
but there is no provision for data types more complicated than 
singly dimensioned arrays. I got comfortable with that level of 
language and when I got into Pascal and C, I didn't stretch my 
capabilities immediately by taking advantage of multi-dimen- 
sioned arrays and structures or records as they are called in 

While I was looking at Modula 2 briefly, I found a use for the 

Union in C or what is called an "alias" in PL/9. That is a way 
to have two different data types occupy the same memory space 
under different names (as aUas implies). This is valuable when 
you want to manipulate, say, a float type variable byte by byte, 
for example to change the exponent for a square root routine 

My project for the near future is to become as conversant with 
the more advanced features of C as is possible, and to take 
advantage of them to write clearer and shorter programs. I'll 
try to demonstrate progress in fiiture discussions. Meanwhile, 
you experienced 'C programmers please bear with me for a 

6809 Assembler Part 2 

Last time we did a first program in Assembler to clear the 
screen of a terminal. What might we do for an encore? There 
is a fairly easy program that we can do that shows a few more 
of the capabilities of calls to FLEX routines. What 1 have in 
mind is a program to calculate and output the sum of two 
numbers included on the command line. For now, of course, we 
will use integer numbers. "Great", you say. "A program to add 
2 and 2". That's right, but in the process we'll look at a few 
more assembler instructions and FLEX calls. Once more we'll 
take it a line at a time and then put it all together. 

We need a litUe background first. There is an assembler direc- 
tive RMB. RMB means Reserve Memory Byte(s). It takes one 
operand or argument, the number of bytes to reserve, and it 
usually is preceded by a label. In our program we are going to 
RMB 2 bytes with the label NUMBER. We have set aside two 
bytes of storage in memory to hold a 16 bit number. This is 
essentially what a higher level language does when you define 
a variable. We have therefore set aside space for the variable 
NUMBER. The label NUMBER is equal to the address of the 
variable NUMBER, and the contents of the two bytes at that 
address is the contents of the variable. This might make more 
sense when we look at the assembler output. 

The X register of the 6809 is a 16 bit register usually used as 
a "pointer", generally called an "Index Register". That is, it 
frequently contains the address of a variable. We use it once as 
such in this program, and once simply as a place to store a 16 
bit value. Here is the program; 


The Computer Journal / #70 


Default origin is $0000, which is OK for this program since we 
don't classify it as a FLEX utility. 


This is another FLEX routine. It outputs a 16 bit value (as a 
decimal number) that is "pointed at" by the X index register. 
More about this below. 



FLEX routine to get a number on the command line (ASCII) 
and translate it to a 16 bit binary number and retiun it in the 
X register. We note here that X is designed as an index register 
but it can just as well hold a value that is being used in the 



This FLEX routine outputs a carriage return and linefeed to the 
terminal. (Print Carriage Return - LineFeed). 



We saw this one last time. It is the JMP address to return to 
FLEX when the program is completed. (WARM Start). 


The RMB directive stands for Reserve Memory Byte. It sets 
aside two bytes in memory at the current address in the pro- 
gram counter. 

Since we didn't specify an ORG, that will be $0000. Since this 
is not a FLEX utility that is as good an address as any for our 
program at least for the time being. Note that RMB sets aside 
memory but it does nothing to initialize the contents of that 
memory. NUMBER is a label that takes the value of the address 
of this variable, in this case $0000. 



This gets a decimal mmiber on the command line and moves 
the command Une pointer along to the next separator (space, 
comma, or CR). The number is translated from it's ASCII 
representation on the command line into a binary 16 bit num- 
ber, and when subroutine INDEC returns, the value is in the X 
register. This program has two labels. START has the value 
$0002, the address of this fust instruction of the program. See 
the assembler output listing later. 



STX stores the value contained in the X register in the memory 
location NUMBER (or we might say in the variable called 
NUMBER). Note the lack of an # sign here. We have an 
instance of an addressing mode we hadn't discussed. It might 

be less confusing if I didn't bring up addressing modes just 
now, but indulge me a little. We'll have a summary at the end 
of this. At any rate, this instruction stores the contents of X at 
the memory location NUMBER that we reserved with the RMB 
instruction above. 



If we are going to add two numbers we need two of them to 
woric on, so we get the second from the command line. Inciden- 
tally since these are 16 bit binary numbers, the values given on 
the command line can't exceed 32,767. Their sum can't exceed 
this value either. (Actually, INDEC can only handle positive 
numbers as well). 



We have one of the values in the memory locations labeled 
NUMBER and the second in the X register. We transfer it to 
the D register. Recall from a few times ago that accumulator 
D is the concatenation of the A and B accumulators, A being 
the high order byte. After this instruction the second argument 
or value is in the D register. 


Ah! Finally we can add the two values. This again is an 
extended address mode instruction. It says to add the contents 
of the variable (the memory with the label) NUMBER to the 
contents of the D register. (You are not seeing triple, the extra 
D is not an error. There is an ADDA and an ADDB instruction 
for the A and B accumulators also. (The index registers can't 
be used for this operation. There is no ADDX instruction, so 
we had to do the TFR X,D fust). The 6809 is very regular in 
it's instructions. The results of any operation like this where a 
value in memory is operated upon by or with a value in a 
register, always ends up in the register. That is, the sum of the 
D register contents and the contents of the memory location(s) 
NUMBER is now in the D register. 



Now we store the sum back in the variable NUMBER, since we 
don't need the previous contents. 


This outputs a CRLF to the terminal and gets us off of the 
command Une so we can print the result on a line Ity itself. 



Now we point X at the variable NUMBER. We have yet 
another addressing mode. The X register is an index register. 
We placed the ADDRESS of the variable NUMBER in it with 
the above instruction. Remember we said that NUMBEP is a 
label that is equated to the address that was RMB'd above. The 
# sign here does mean "immediate". 

The Ck)mputer Journal / #70 




Now with X "pointing at" NUMBER, we call the FLEX rou- 
tine that translates the 16 bit value pointed at by X to an ASCII 
string and prints it to the terminal. (OUT DECimal). 


Let's put the result on a line by itself by doing another CRLF. 

ReUim to FLEX 



(fousekeeping telling the assembler that the program starts at 
the label START. 

How do we run the program after it is assembled? Supposing 
that the working drive is 1, the assembler de&ult output file 
extension is .BIN so we run the program with the command: 

1.ADD.BIN 123 456 <cr> 

The result is printed on the next line, 579. You can copy 
ADD.BIN to your System drive and rename it ADD.CMD. 
Then the program can be run with the simple command ADD 
123 456 <CT>. Rather than just printing the listing without the 
explanation between every line, I'll show the assembler output: 














0000 NUMBER 

















IF 10 




D3 00 




DO 00 


























I am presentiy having a bit of trouble transferring assembler 
ou^ut files inqrarted into a 6809 text file and then moved to 
a PC formatted disk. It is necessaiy to add a Unefeed to every 
line since FLEX terminates lines with CR only and the PC 
expects a CR fdlowed by an LF at the end of every line. Most 
of the trouble was that my filter program is not quite right yet 
and it collapsed the assembler listing, removing all spaces from 
every line. I will fix it. Meanwhile I don't guarantee that the 
above listing is formatted just as the assembler output is. 

There are several things to talk about here. First, NUMBER 
was given two memory bytes at address $0000. The label 
START is at the address $0002. The assembler did sometiiing 
automatically for me that I hadn't mentioned. It used a special 

short addressing mode in the instructions ADDD NUMBER 
and STD NUMBER. Since number is at address $0000 it used 
the direct page addressing mode. This is a special mode that 
meant a great deal back in the days of 4K memory. If you put 
your variables all on one page (in this case addresses $0000 
through $00ff) they could all be reached using a single byte 
address rather than a two byte address. (A page is defined as 
all the memory that can be accessed with an 8 bit address. That 
number is 256 bytes). Thus every reference to the variables 
saved a byte compared to extended addressing mode. The 6809 
has a Direct Page Register that can be set to any page in 
memory. When the processor is reset by power on, it resets to 
$00. Sometimes you can make use of this to squeeze a program 
size a bit. Actually the direct addressing mode saves a few 
clock cycles too, so the program will run a bit faster. Let's look 
at the addressing modes we have "tripped over" so far: 

Direct STA $10 Stores contents of A at $(DP) 10, i.e. the 
DP register holds the upper byte of the address for the STA 
instruction. Extended STA SIOOO Stores contents at $1000. 
Immediate LDA #$56 Loads the value $56 into the accumu- 

Excuse me if I seem to be repeating myself here. I am trying 
to say everything a number of different ways and to repeat as 
much as possible. When I was learning how to program I was 
confused over the immediate addressing mode for a long while, 
so I'll repeat. Using labels seems to add to the confusion, so 
let's do it with numbers first and then with labels: 

LDD #$1234 Loads ACCD with tiie hexadecimal value 1234. 
LDD $1234 Loads ACCD with Uie CONTENTS of memory 
address $1234. LDX #NUMBER loads X with the value 
assigned to the label NUMBER. In the case of the above 
program $0000. LDD NUMBER would load D with tiie con- 
tents of tiie variable NUMBER. 

Note that the immediate addressing mode doesn't make sense 
for store operations, only for load or add or such. Immediate 
values can be thought of as program "constants". 

We've kind of half looked at the "indexed" addressing mode 
too. We didn't use it explicitly in our program but OUTDEC 
required us to set up X as a pointer to the variable NUMBER. 
Note tiiat tiie label NUMBER has the value $0000 and the label 
START has the value $0002 (see the assembler output listing 
leftmost column). The instruction LDX #NUMBER therefore 
loads X with the value $0000. If we had left out the # sign (a 
common error) it would have loaded X with the contents of the 
variable, our sxun, 579 decimal. OUTDEC wants X to contain 
the address of the number to be output, not the value of the 
number, so we had to use the immediate mode. Perhaps I've 
said that enough times in enough sUghdy different ways. 

Down the line we will complicate things a bit more when we 
talk about position independent code and putting variables at 


The Computer Journal / #70 

addresses that are tied to the program address. When this is 
done, the program can be loaded anywhere in memory and it 
will run there. For now, let's try to keep it a little simple. 

As we get into more complex programs you will notice that 
about half of the instructions involve the LD or ST instruc- 
tions, i. e. LDA, LDB LDD LDX LDY LDU LDS and STA 
STB STD STX STY. These are memory reference instructions. 
They cause information to be moved from memory to a register 
or from a register to memory. There is the TFR instruction to 
transfer data from one register to another and the EXG instruc- 
tion that EXchanGes values between registers. When we use an 
LD instruction to get a value from memory, that value in 
memory is imchanged. Only the value in the destination reg- 
ister changes. Similarly when we store a value to memory, the 
value in the source register doesn't change, only the value in 
the destination memory locations. Load and store are not the 
only memory reference instructions. We used ADDD for ex- 
ample. That instruction added the contents of a memory loca- 
tion to the D register, again leaving the memory value alone 
and only modifying the contents of the D register. To save the 
result, we had to store it in memory again. 

If you are following this series let me say that an hour of 
practice is worth a year of reading. For example, you could 
enter the above program and assemble it. Try it out and when 
you get tired of seeing the sum of two numbers, see if you can 
modify it to add three numbers. Some time we'll extend it to 
add any string of numbers until you enter zero. 

Don't be fooled. We've used a couple of rather powerful FLEX 
routines to do some things that would take a lot of code to do. 
Adding the two numbers is no chore, but converting the input 
ASCII string to it's binary representation and converting the 
sum back to an ASCII string are non-trivial operations. Per- 
haps we can write our own down the way a bit and show how 
it might be done within FLEX. Generally if you want to keep 
a program small and simple, it is advantageous to use operat- 
ing system calls as much as possible. They only cost a few bytes 
in the way of a JSR to an extended address! 

I have a few more of what my daughter calls "factoids" for you 
concerning the 6809, and for that matter all of the Motorola 

1) Values larger than one byte are stored highest order byte in 
lowest memory, (what I generally think of as "left to right" 
order). That is, as you progress through memory counting from 
low addresses to high, you encounter 16 bit and floating point 
values with the high order byte first. This is backwards from 
what the Intel processors use. (I'll resist the temptation to say 
that Intel does it backwards)! It has caused me no end of 
frustration when I first started to work with manipulating 
numbers in memory in a PC environment. Strangely both the 
6809 and the Intel processors store strings with the first letter 
in the lowest memory. That is, a string and a number read "low 
to high" in a Motorola processor envirorunent, but in the Intel, 
a string reads low to high memory but a number reads high to 

low. (If I remember correctly, the 6502 stores 16 bit values in 
the same order as the Intel processors). 

2) 16 bit values may be stored at either even or odd addresses. 
The 6809 doesn't care. You can store the contents of X at 
address $0101 or at $0102. It doesn't matter. This is NOT true 
of the 68000 where 16 and 32 bit values must be stored at even 

More on C 

A while ago I did a little note on C, and using arrays vs 
pointers. My words drew a letter from Richard Brewster (Issue 
67) saying that source code using arrays truely generates more 
object code than source code using pointers. I guess I can say 
that the book that I quoted lied! (It basically said that the 
compiler would convert array notation into the same object 
code as pointer notation). I'm convinced. That was written 
several months ago. Since then I agreed to teach an informal 
class in C so I dug up two tutorials and did a lot of reading. I 
am begirming to feel comfortable writing a program in C and 
expecting it to work rather quickly if not on the first try. 1 
understand pointer notation in C, and did when 1 wrote the 
above, but understanding it, feeling comfortable using it, and 
having it's use be second nature (like riding a bicycle or 
driving a car) are three different things. I am about at the 
second of those three stages now. 


Detroit has a morning radio show host named J. P. McCarthy. 
One morning this week he was talking to someone about a 
"roast" at which he is to be the "roastee". He mentioned a high 
price per plate at the event and then added that it would, of 
course, be "a benefit for the hungress and homely". Next try it 
came out "hungress and homeless", and not until the third try 
did it come out right as "hungry and homeless". I chuckled all 
the way to work! I got to thinking about what a benefit for the 
homely might entail... a grant for plastic surgery? Masks? 
Maybe I could qualify for one or the other. 

A friend of mine who sang regularly on the radio (WMBI in 
Chicago) once was singing "The Lord's Prayer" and because 
of previous fooling around with the words, they came out 
"Lead us not into Penn Station" ! He said he would never more 
play with the words. He got to that point and then just couldn't 
remember which was correct! 

Lastly, 1 once worked at the University of Illinois School of 
Chemical Sciences. That school had a very nice hard working 
cooperative business manager named Larry Hess. We got to 
calling him Harry Less (or was it Hairy Les) privately, and one 
day one of the staff called the business office and, of course, 
asked for Harry Less. "You mean Larry Hess", chuckled one of 
the secretaries. Hopefully she thought it was just a slip of the 
tongue, but we stopped our private joke! 

The Computer Journal / #70 


Special Feature 

Intermediate Users 

Parts: Serial 1/0 


by Brad Rodriguez 

At long last, the final installment of the "Scroungemaster 11" 
multiprocessor. I may in the fiiture write some software articles 
around this board — a 6809 Forth is certain — but this wraps 
up the hardware description. Go, and prototype! 


Figures 1 and 2 contain the two UARTs which provide four 
serial ports for the Scroungemaster II. Since these circuits are 
nearly identical, I will discuss them together. Afterwards 1 will 
mention the differences. 

UIO and Ull are Zilog Z8530 Serial Communications Con- 
trollers (SCCs). These are very versatile chips, each of which 
includes two serial ports and two programmable baud rate 
generators, plus some miscellaneous 1/0. All of the common 
asyiKhronous formats are supported, plus many synchronous 
ones (see sidebar). The 4 MHz part will transfer data at i^ to 
1 Mbit/second. (I'm told Apple uses this chip for the Appletalk 
network in the Macintosh.) 

UIO is enabled by chip select 100\, and Ul 1 by 101\. Each chip 
looks at only the low two address lines, so each occupies four 
consecutive locations in memory. As wired here, the SCC 
registers appear as follows: 

UIO (Ull) address 
FFCOl (FFC81) 
FFC02 (FFC82) 
FFC03 (FFC83) 


Port B (D) command 
Port B (D) data 
Port A (C) command 
Port A (C) data 

(Remember that these are addresses in the mapped 1 MB 
memory space.) The ports of each chip are called A and B in 
the Zilog documentation. On the Scroungmaster 11 board I 
refer to UIO as ports A and B, and Ul 1 as ports C and D. If 
only two serial ports are needed, Ull can be removed. 

The serial ports of most personal computers use signal levels 
adhering to the Electronics Industries Association (EIA) RS- 
232 standard. This standard specifies a voltage of -5 to -15 
volts for logic "1", and +5 to +15 volts for logic "0" [P1P85]. 
U26 and U25 generate and receive RS-232 levels for the 
Scroungemaster II. U26 is an LM1488 quad RS-232 driver, 
and U25 is an LM1489 quad RS-232 receiver. Only the Re- 
ceive Data (RXD) and Transmit Data (TXD) from each serial 

port are converted to RS-232 levels. (The RS-232 standard 
specifies a number of control signals, such as DCD, DTR, 
DSR, RTS, and CTS, all of which must use these same logic 
levels. This board does not support these signals.) 

Note that if and only ;/RS-232 drivers are used, +12v and -12v 
power supply voltages must be provided. (Everything else runs 
on +5v only.) 

RS-232 is limited to short cable runs, relatively low data rates, 
and point-to-point connections. To allow higher data rates or 
longer cables, EIA defined the RS-485 standard. RS-485, an 
improved version of the earlier RS-422, uses balanced trans- 
mission, which means that each signal is carried on a pair of 
wires: one wire carries the "true" signal, and the other wire 
carries its logical inverse. Signal levels are approximately 5 
volts and volts, but the detailed specifications of RS485 
require the use of special driver chips and not just TTL outputs. 
The Scroungemaster II uses a 75174 quad RS-485 driver 
(U13), and a 75175 quad RS-485 receiver (U12). Again, only 
the serial RXD and TXD are converted to these levels. 

Important: On this board, the choice of RS-232 vs. RS-485 is 
made by which pair of driver chips you install. This means that 
the four ports may be all RS-485 or all RS-232, but you can't 
have a nux of RS-485 and RS-232. Do not install both sets of 
drivers! Install only U12/U13, or U25/U26. 

Another advantage of RS-485 is that it allows multidrop opera- 
tion, in which several serial ports are connected to one pair of 
wires. When you connect a network of CPUs in this way, any 
CPU can talk to any other (and you can also save a lot of wire!). 
For this to work, though, only one CPU can drive the wires at 
any one time. The other CPUs must have their RS-485 drivers 
disabled, i.e., in a high-impedance state, so they neither drive 
nor load the serial "bus." (The problem of deciding when each 
CPU can enable its driver is worth several more articles, and 
I won't talk about it here.) 

The 75174 chip (U13) is somewhat unusual in that its RS-485 
drivers are enabled in pairs. (There are only two enable inputs 
for the four drivers.) This means that you can't use all four 
Scroungemaster II serial ports for multidrop, since each 
multidrop port needs an independently controlled transmitter. 
I've arranged the drivers so that ports A and C are enabled 
together, and likewise B and D. This means that if you have 


The Computer Journal / #70 

only one SCC installed (UIO), you have two fully-functional 
multidrop RS-485 serial ports. If you install both SCCs, you 
can run all four ports RS-485 point-to-point (since for point- 
to-point (^ration you leave the driver always enabled). Or you 
can run two ports point-to-point and one port multidrop (e.g. 
B and D point-to-point, A multidrop, with C unusable because 
it's driver is enabled according to A's needs). 

The A and C drivers are enabled when the RTSA\ output of 
UIO is high. The B and D drivers are enabled by RTSB\ of UIO. 
(Thus Ul 1 is optional in a two-port system.) The RTS\ outputs 
must be controlled by software. The RS-485 receivers are 
always enabled. 

The serial signals are brought out on 10-pin headers such that 
two ports may be connected together by putting a half twist in 
the ribbon cable: 

pin signal signal pin 

1 CTS\ <-> RXRDY\ 10 

2 RXC <-> TXC 9 

3 GND <-> GND 8 

4 RX- <-> TX- 7 

5 RX+ <-> TX+ 6 

6 TX+ <-> RX+ 5 

7 TX- <-> RX- 4 

8 GND <-> GND 3 

9 TXC <-> RXC 2 

10 RXRDYX <-> CTS\ 1 

In other words, a half twist serves as a null modem. (If RS-232 
signals are used, the signals appear oh the TX- and RX- pins.) 

TXC and RXC are the serial clock output and input, respec- 
tively, of the serial port. (Strictly speaking, TXC can be pro- 
grammed to be either an output or an input, but only the former 
is usefiil here.) If the TXC of one port is connected to the RXC 
of another, the two ports can use the xl clock mode, and all 
synchronous modes. This is intended for 1 Mbit/sec operation 
between adjacent CPUs. TXC is not buffered, so the cable 
length can be only a few inches. 

Inverters U9C through U9F generate "Rx ready" signals that 
I hope will allow automatic flow control between two con- 
nected serial ports, as follows: The SCCs W/REQ\ pin can be 
programmed to go low when the receive buffer contains a 
character C'DMA Request on Receive" mode). Thus, when the 
receive buffer is empty, W/REQ\ is high and RXRDY\ is low. 
This is connected to the CTS\ input of the "sending" SCC, 
which should be programmed in the "Auto Enables" mode. In 
this mode, a low on CTS\ enables the transmitter, and a high 
disables the transmitter (after it finishes sending any character 
in progress). This scheme is still to be tested, but if it works, 
it will i»event one serial port from "ovemmning" the other. . . very 
handy at 1 Mbit/second! Note that the RXRDY signals are not 
buffered, and, like the clock signals, are only usable over short 

Only the RX and TX signals should be run over long distances 
(up to 50 feet for RS-232, or 4000 feet for RS-485). In the 
absence of the clock signals, use a x 16 or x64 asynchronous 
mode, or use the DPLL for clock recovery in synchronous 
modes. (For further details refer to the Zilog technical manual.) 
Flow control must be done in software. 

You can run the clock and flow control signals long distances 
if you provide suitable external drivers (RS-232 or RS-485). 
You may also want to add external logic functions or level 
translation (say, to produce a MIDI port). To ifacilitate this, pin 
10 of the serial connector can be jumpered to +5 volts (JPIO- 
JP13). Of course, you lose the RX Ready signal if you do this. 

The DTR\ pins of the SCC can be used as general-purpose 
outputs. These two outputs from UIO provide as the the TASK 
and SWREQ\ control signals, used elsewhere in the 
Scroungemaster II. (Another reason why you should keep 
UIO, and not UU, if you need only two serial ports.) 

The DCD\ pins of the SCC can be used as general-purpose 
inputs. These can also be programmed to generate an interrupt 
whenever the level changes in either direction. So, these two 
inputs on UIO are used for SWGRANT\ and rRQ4\. But in the 
Auto Enables mode, the DCD\ inputs must be grounded to 
enable the SCC receivers. This can be done with JP14 and JP15 
(disabling the SWGRANTV and IRQ4\ fimctions.) 

The DTR\ and RTS\ pins of Ull have no assigned function, 
and so are brought out to a 4-pin header. The DCD\ pins are 
permanently grounded on Ul 1. 

JP7 and JP8 control interrupt assignments of the SCCs. Along 
with JP9 and JP4, which control the PIO and PC bus interrupts 
(respectively), they allow the following possible assignments: 












IRQ4 (via UIO) 

All three I/O chips may have distinct interrupts, which makes 
for the simplest interrupt routines. Either or both SCCs may 
use the 6809 's fest interrupt (FIRQ) for high data rates; but of 
course, when two chips share an internq)t, your software must 
poll them to identify which is generating the interrupt. Also, 
if a chip is connected to the Non-Maskable Interrupt (NMI), its 
interrupt carmot be disabled by the CPU — it only be disabled 
by writing to that chip's interrupt control register. (Both the 
SCC and the PIO have such a register.) 

If you are using PC bus interrupts and all three I/O chips, then 
two of the four interrupt sources must share one of the three 
6809 interrupts (and polling must be used). Or, you can route 
the PC bus interrupts to "1RQ4" (UlO's DCDB\ input), in 
which case PC bus interrupts will be processed through UlO's 
interrupt logic 

The Computer Journal / #70 



Whenever I design a CPU board, I always include at least one 
LED — the most useful tool for bringing up a new (or dead) 
board. By popular demand, the Scroungemaster 11 has eight 
programmable LEDs, in a 10-segment bargraph, Dl. (The 
middle two segments are used as a power indicator.) Octal 
latch U23 (74HCT377) serves as an 8-bit parallel output port, 
selected by I03\ (mapped address FFD80). When a "0" is 
written to any bit of this output port, the corresponding LED 
will illuminate. For simplicity, the LEDs share a single current 
limiting resistor, so the more LEDs you turn on, the dimmer 
they get. A 74HCT377 is recommended instead of a 74LS377 
because of the HCT part's greater current capacity. 


One of the experiments I want to perform with my multipro- 
cessor system is having one processor interrupt another, as a 
method of signalling. U29 and U30, if installed on one CPU 
board, make a programmable interrupt generator. The com- 
parator U29 (74LS688) identifies when a write occurs to any 
I/O address (X)0-007 on the IBM PC bus. (In IBM PCs, these 
addresses are reserved for the motherboard, so we know no 
plug-in peripheral card will ever use them.) When such a write 
occurs, the programmable latch U30 (74LS259) writes the data 
bit XDO into one of eight latches. Which of the eight is selected 
by address bits XA0-XA2. 

The eight latches output to interrupt lines IRQ0-IRQ7. Each of 
the ei^it possible CPUs can be jumpered to one of these lines. 
So, if CPU #5 is jumpered to receive IRQ5, you can interrupt 
this CPU by writing a "1" to PC bus I/O address 005. (Recall 
that this appears as mapped address DFC05 to the 6809. Also, 
PC bus interrupts are active high, so writing a "1" asserts the 
interrupt, and a "0" removes the interrupt.) Since U29 and U30 
are electrically connected directly to the IBM PC bus, and not 
to the board's "internal" bus, any CPU can write to them. So, 
by installing U29 and U30 on one board, and jumpering the 
interrupts appropriately, any CPU can interrupt any other. 

Normally, U29 and U30 will be installed on the bus master. 
These should not be installed if IBM PC peripheral cards will 
be generating interrupts. This is because U30's outputs are 
always active — like many PC perhiperals — and if one board 
is pulling an interrupt line high while another pulls it low, 
someone's drivers will be damaged. 


When designing microprocessor circuits, it's not enough to get 
the voltage levels and the logic right. You have to get the 
timing right, too. Timing q)ecifications are published by the 
manufacturer (usually in the data books, e.g. [MOT83, TEX85, 
ZIL88]) for all microprocessor and logic chips. These specs 

a) when each input is required, 

b) when each output is valid, and 

c) how long the chip will take to perform a given function. 
While automated tools exist which will analyze the timing of 
any digital circuit, many engineers still do it manually by 
constructing a timing diagram. 

Figure 3 is a partial timing diagram for the Scroungemaster II. 
The timing is shown for the fastest CPU (68B09 with an 8 MHz 
oscillator) and the slowest recommended "glue" logic (74LS 
TTL). This is usually the "worst case" for timing analysis, 
since the CPU imposes the "deadhnes" while the glue logic 
introduces the "delays." If any part of the logic adds too much 
delay, I can replace chips with a faster equivalent (74ALS, 
74AS, or 74F TTL). Important: although supposedly equiva- 
lent, many 74HCT parts are actually slower than 74LS. If you 
want to use 74HCT, verify the timing first. Better still, use the 
faster 74HCTLS, 74 ACT, or 74AHCT families. Also, you may 
be able to substitute "plain" 74 or 74S family parts in some 
places, but beware of their much higher power consumption. 

Each line of Figure 3 represents one signal (or a group of 
signals with idenUcal timing). The horizontal axis is time; 
each division is 50 nsec. Only the most critical signals are 
shown. For many devices (e.g. RAM and EPROM) you can 
compare the timing requirements of the chip directly with this 
diagram — you don't need to draw every signal. 

The first line is the 6809 E signal. The "falling edge" of E 
(from +5 V to OV) is the start of a 6809 memory cycle, and is 
the "reference point" for most of the timing specs, so I have 
drawn the diagram with time T=0 at the falling edge. Note 
that, according to Motorola specs, E could be low for as little 
as 210 nsec. Thus I've drawn the rising edge of E to span a 
range from T=2 10 to 250 nsec. During this "window", E could 
rise at any time, so we don 't know for sure whether E will be 
high or low. 

The second line is the 6809's "quadrature" clock signal, Q. If 
the falling edge of E is T=0, then Q will rise between times 
T=80 and T=125 nsec. Although the Scroungemaster II doesn't 
use the Q signal, some of the 6809 signals are specified relative 
to Q, so it needs to be on the diagram. 

The 68B09's address and R/W\ lines are guaranteed to be valid 
and stable 15 nsec before the rising edge of Q. They remain 
stable throughout the cycle, and 20 nsec into the next cycle, 
i.e., 20 nsec after the next falling edge of E. (Obviously, for the 
first 20 nsec of this cycle, address and R/W\ carry "old" data.) 
On the diagram, I have "X'ed out" the period when these lines 
are changing (and thus unknown). Also, when they are stable 
they could be high or low — the address could be anything! — 
so I've drawn both signal levels (0 and +5) during this period. 
These are common conventions used in timing diagrams. 

The 68B09 requires that data read from memory or 1/0 be valid 
40 nsec before the start of the falling edge of E. Because of E's 
rise and fall times, this edge could be as soon as T=470 nsec, 
so data must be stable at T=430 nsec. Also, this data must 
remain stable imtil 10 nsec after the end of the falling edge of 


The Computer Journal / #70 

E, i.e., until T=510 nsec. This is a need 
be satisfied. 

a requirement to 

The 68B09 guarantees that data written to memory or I/O will 
be valid 1 10 nsec after the rising edge of Q, and will remain 
valid until 30 nsec after the next falling edge of E. On this 
diagram, this is from T=235 to T=530 nsec. This is a given — 
a known timing characteristic of a signal. 

Now we can analyze the Scroungemaster n circuit. First, look 
at the memory mapping and decoding schematic. All of the 
address and control inputs to the 74S189's are stable at T=l 10 
nsec. The 74S189 takes at most 35 nsec to access its data, so 
its outputs (and thus the "mapped address") are valid at T=145 

The WRMAPV and OEPROM\ signals are derived from A15, 
R/W\, and E. You can see that A15, RAV\, and the inverted 
R/W\ (U7D) will be stable long before E goes high. So E is the 
deciding fector, and the WRMAPV or OEPROM\ signal will go 
low 10 to 15 nsec after E goes high (assuming that the CPU is 
writing the map or reading the EPROM, respectively). WRMAP\ 
or OEPROMX will remain low until 10-15 nsec into the next 
cycle. This is the propagation delay of a 74LS10 NAND gate. 

The second stage of decoding, U4 and USA, produces the 
signals IOZONE\and ONBOARDV These signals are logically 
derived from the CPU address and the mapped address, and we 
know the CPU address must be stable before MA12-MA19 can 
be stable. So lOZONEV and ONBOARD\ will be stable at 
T=160 nsec, 15 nsec (the maximum delay of the NAND gates) 
after the mapped address. In this case we're not worried about 
the minimum delay of the NAND gates (which would tell us 
how soon IOZONE\ and ONBOARD\ could possibly be as- 
serted). Both of these signals will remain stable xmtil the 
address changes, at least 20 nsec into the next cycle — which, 
we will see, is sufficient. 

IOZONE\ is the last input of U24 to become stable, so U24's 
outputs — the IOn\ select lines — will follow IOZONE\ by 32 
nsec, the maximum delay of the 74LS138. Similarly, the 
OFFBD\ signal (U6D) follows ONBOARD\ by 15 nsec. 

The read and write strobes, however, are not output by U5 until 
E goes high. You can see from the diagram that all the other 
inputs of U5 will be stable before the rising edge of E. So, the 
various read and write strobes will trail E by 14 to 26 nsec (the 
propagation delay from the 74LS138's Gl input to its outputs). 
In tiiis case we want to know upper and lower bounds on the 

The next two lines show transitions propagating through the 
memory request logic. If the bus is not available, MRDY will 
be pulled low no later than time T=250 nsec. For MRDY to 
stretch a memory cycle, the 68B09 needs to see it pulled low 
no later than T=360 nsec (110 nsec before the falling edge of 
E). You can see that, even in the worst case, we have 1 10 nsec 
to spare! 

If we're doing a three-cycle stretch, we can't have glitches on 
the REQ signal (NAND gate U6A). To ensure this, STRETCH\ 
must go low before OFFBD\ goes high. STRETCH\ will go low 
no later than T=520 nsec (20 nsec after the falling edge of E). 
We know that OFFBDV follows ONBOARD\, which follows 
the mapped address, which follows the 68B09 address, which 
remains valid 20 nsec into the next cycle.. .so there's no prob- 

We can control (via JP6) how much extra delay is added to a 
bus cycle when the 6809 has to wait for ownership. What 
happens if this CPU already owns the bus? The next six lines 
of the timing diagram show that DRIVENBU is asserted (low) 
at T=205 nsec. The address will then be output to the bus no 
later than T=235 nsec, and the bus RD\ and WR\ strobes will 
be asserted no later than T=3 10 nsec, and will be at least 185 
nsec wide. Read data must be valid on the bus no later than 
T=420 nsec, to allow for a 10 nsec delay through the bus buffer. 
Write data will be vaUd on the bus no later than T=245 nsec. 
Finally, if a bus peripheral (such as a CGA card) wants to 
stretch the memory cycle, it must assert lORDY no later than 
T=330 nsec. (Does this meet the specs of PC peripherals? Who 
knows? Only experimentation will tell.) 

We now have enough information to determine if any given 
memory or I/O chip will work with the Scroungemaster II 
CPU. The first example shown is the Z8530 SCC chip. (This 
analysis is also valid for the Z8536 parallel I/O chip, since it 
has nearly identical timing requirements.) For convenience, I 
have duplicated the Unes showing the read and write strobes 
and the IOn\ selects. 

The Z8530 requires that its address lines be valid from T=125 
to T=520 nsec. Since AO-Al come from the CPU, we can see 
that this requirment is met. 

If this chip is to be accessed, the Z8530's CE\ input (IO0\ or 
10 1\) must go low before RD\ or WR\ go low, and must stay 
low as long as RD\ or WR\ is low. (As Zilog specs it, CE\ must 
go low at least nsec before RD\ or WR\ goes low, and must 
stay low at least nsec after RD\ or WR\ goes high.) This 
requirement is met with time to spare. If this chip is not to be 
accessed, CE\ must be high at least 100 nsec before RD\ or WR\ 
goes low.. .which means that the IO0\ or I01\ select must not 
stretch more than 125 nsec into the next cycle! Again, no 

The 8 MHz Z8530-8 will output read data no later than T=430 
nsec (140 nsec after its RD\ goes low), which exactly matches 
the 68B09's need. This data will remain valid at least 14 nsec 
— the delay of U5 — after E fells; the 68B09 needs it to be held 
only 10 nsec after the fall of E. This is a case where using a 
faster logic family (for U5) could theoretically introduce a 
timing problem! 

The Z8530 parts are peculiar, and perverse, in requiring write 
data to be vaUd before the falling edge of WR\. 10 nsec \ sfore, 
to be precise. If the decoding logic is ruiming near its astest 

The Computer Journal / #70 


spec, WR\ could be asserted as soon as T=220 nsec. But the 
CPU doesn't guarantee write data until T=235 nsec! This 15 
nsec discrepancy can be resolved several ways: 

a) hope that the 68B09 and Z8530 timing specs are sufficiently 
conservative to cover this 15 nsec discrepancy (e.g., the 68B09 
may output data sooner); 

b) hope that the decoding logic operates near its nominal 
timing and not its minimum timing specs (another case where 
faster logic spells trouble!); 

c) add some gates to delay the RD\ and WR\ signals, being 
careful not to violate the data hold time spec; or 

d) use the CMOS Z85C30, which intelligently latches its write 
data on the rising edge of WR\. 

So fer I've had good luck relying on (a) and (b). If I run into 
problems, (d) is an easy out. If I were being paid for this I might 
expend the extra effort to do (c). But note that the write data 
must be held at least as long as WR\ is low, and that WR\ can 
go back high as late as T=525 nsec. The 68B09 holds write 

data until T=530 nsec. Any delaying circuit must therefore 
delay the falling edge of WR\, but not the rising edge! 

The second example is the 2 MHz 6522A Versatile Interface 
Adapter. This was briefly considered for the SM II's parallel 
I/O. You can see the problem with this chip immediately: it 
requires that its CS\ be valid at T=130 nsec (80 nsec before the 
rising edge of E). But the IOn\ select lines are not valid until 
T=192 nsec! This 62 nsec discrepancy is too big to ignore, and 
there is no way to fix it short of putting the 6522A into the 
"unmapped" memory space... a solution I did not want to use. 

Observe also that the 6522A provides read data 10 nsec too late 
for the 68B09. There's no easy way to fix this, since this is a 
190 nsec delay from the rising edge of E. If it had been a delay 
from some other signal, we could try to provide that other 
signal sooner (e.g., with faster logic). As it is, we can only use 
a &ster part.. .and a faster 6522 doesn't exist. 

I conclude that 74LS logic can be safely used throughout the 


In parallel data tnnsmission, such as on the PC bus, several data bits are 
put on several wires at the same time, and there are usually additional wires 
to control the timing of the transfer. When you want to send data over a 
single wire, you have to send the data bits one at a time, or serially. Serial 
transfer opens a whole new can of timing and control problems. 

Usually, the bits will be placed on the wire one at a time, for a fixed period, 
starting with the least-significant bit (DO). The baud rate is the reciprocal 
of the bit period, so that at 9600 baud, each bit is placed on the line for 1/ 
9600th of a second. (For all our purposes, anyway, you can fmd a more 
detailed discussion in [ARR93].) Both ends of the serial link use a crystal- 
controlled clock to measure the bit period accurately. 

But when does this bit period start...and in a continuous stream of data, how 
do we identify the first bit of a new byte? 

In asynchronous transmission, each byte can be sent independently ("asyn- 
chronously"). Between bytes, the wire is held at a steady logic "1". To 
signal the start of a byte, a logic "0" is placed on the wire for exactly one 
bit period This is called the "start bit." The 1-to-O transition marks the 
"edge" of the bit period, and all succeeding bit periods can be timed from 
that reference point Even if the two ports' clocks are a few percent 
different, the accumulated error over eight bits is small enough that the bits 
can be recovered. But over several bytes the error will build up, so after 
each byte a logic "1" is output for one or two bit periods — one or two 
"stop bits." Having a stop bit means that the next byte will always start with 
a 1-to^ transition, resynchronizing the bit timing. (Two stop bits were 
required in the days of mechanical teletypes. Electronic serial ports get by 
fine with just one.) 

From five to eight data bits can be sent between the start and stop bits (least- 
significant bit first). After the data bits, and before the stop bit, can be an 
additional bit called the parity bit. The parity bit is designed to make the 
total number of "1" bits either Even or Odd. If one bit is received incor- 
rectly, the parity will be wrong, causing a "parity error." (The parity 
schone thus detects all "one-bit errors." If two bits get flipped, the parity 
is unchanged.) Sometimes the parity bit is forced to "0" ("Space") or "1" 
("Marie"), or is omitted entirely ("None"). So, when you see an IBM PC 

set up for "9600,N,8,r', you can now read that as "9600 baud. No parity, 
8 data bits, 1 stop bit." 

In synchronous transmission, the transmitter clock is connected to the 
receiver, and the bytes are sent in a continuous uninterrupted stream, without 
start and stop bits. Once the starting point is found, we simply read every 
eight bit periods as a new byte — there had better not be delays between the 
bytes! To identity the starting point we send a synchronization (sync) 
character — a unique bit pattern that we can detect as bits are shiited 
through the receiver. (It's also possible to use a separate sync signal, but this 
is uncommon.) One advantage of synchronous transmission is that it's 20% 
faster — a byte is sent in eight bit periods, and not ten (eight data + one start 
+ one stop). 

Sometimes you don't need to physically connect the transmitter clock to the 
receiver. A digital phase-locked-loop (DPLL) such as contained in the Zilog 
sec can synchronize the receiver almost perfectly to the transmitter, pro- 
vided that there are frequent 1-to-O or O-to-1 transitions in the data. There 
are several ways to ensure this. One software scheme is group-coded record- 
ing (OCR), used in Apple floppy disks. One hardware scheme supported by 
the sec is the synchronous data-link control (SDLC) protocol. 

The hardware can also add extra transitions to the bit stream, to make "clock 
recovery" easier. Among the methods are FM (frequency modulation, also 
called "bi-phase" encoding), MEM (Modified FM), and Manchester encod- 
ing. (MFM is used for double-density floppy disks and many hard disks.) 
The details are too long to relate here; just be aware that the Zilog SCC can 
send and receive FM, and can receive Manchester encoded data. [Z1L86] 

The bit timer (in asynchronous modes) and the DPLL (in synchronous 
modes) run from a crystal-controlled timebase (a programmable counter 
called the "baud rate generator"). If the timebase is 16 times faster than the 
bit period, then the bit period can be counted off in 16 steps — we can say 
that the timing resolution is l/16thofabit. Thisiscalleda"16x"(16-times) 
clock. In its various modes, the Zilog SCC can use a 64x, 32x, 16x, or Ix 
clock. If a Ix clock is used, the receiver has to be synchronized perfectly to 
the transmitter (by a physical connection), since the timer can't be "tweaked" 
in fractions of a bit. This is why the Scroungemaster 11 serial ports allow the 
receivCT to be connected to the transmitter clock. 


The Computer Journal / #70 

SM n, even with the faster CPU. I make the (perhaps unjus- 
tified) assumption that if 74LS logic is fast enough for the 
68B09, the 1.5 MHz 68A09 and the 1 MHz 6809 will pose no 
problem. In view of the timing discrepancies of the Z8530, 1 
may be too hasty assuming this, and I should do a fresh 
analysis at 1 MHz. I suspect that with the slower CPUs, the 
slower 74LS189 can be used instead of the 74S189 in the 
memory mapping logic. (The last time I checked, though, the 
74S189 was still less expensive.) I'll leave these as exercises 
for the student, and I'll be interested to hear from you. 


Listing 1 is a simple test program for the Scroungmaster II, 
written for the PseudoSam Level 1 freeware assembler (A6809). 
It begins by initializaing the memory mapping registers (which 
are in a random state on power-up). It then counts in binary 
from to 255 on the LEDs, initializes one SCC (UIO), and 
enters a loop of receiving and sending characters on serial port 
A. The serial port will run at 4800 baud with the basic 4 MHz 
oscillator, or 9600 baud with an 8 MHz oscillator (requiring 
68B09 CPU and Z8530-08 SCC). Either an 8Kx8, 32Kx8, or 
128Kx8 static RAM must be installed for the serial initiahza- 
tion subroutine to work. 


[ARR93] American Radio Relay League, The ARRL Handbook for 
Radio Amateurs. ARRL, Newington, CT (1993). A new edition is 
published every year. One of the best references for electronics and 
radio, but rather weak on computers and digital stuff — except for 
communications, naturally. For some reason the ARRL thinks that 
"baud" has a plural, "bauds." 

[MOT83] Motorola Inc. 
eral Data (1983). 

Motorola 8-Bit Microprocessor and Periph- 

[PIP85] Pippenger, Tobaben, et al.. Linear and Interface Circuits 
A pplications. Volume 2: Line Circuits. Display Drivers . Texas In- 
struments (1985), ISBN 0-89512-185-9. An excellent sourcebook 
which, alas, may no longer be available from Texas Instruments. 
Well worth finding. 

[TEX85] Texas Instruments Inc., The TTL Data Book. Volume 2 

[ZIL86] Zilog Inc., Z8030 Z-BUS SCC / Z8530 SCC Serial Commu- 
nications Controller Technical Manual (September 1986). Essential 
if you want to do anything fancy with the SCC. 

[ZIL88] Zilog Inc., Z8000 Family Data Book (November 1988). 

.command -ai ; output in Intel hex format 

Listing 1 . Test program for Scroungemaster II. 
Can be run from a 2764, 27128, or 27256 EPROM. 

; 6809 reset vector 
.org h'fffe 
.dw entry 

; program addresses of on-t)oard I/O, 

wtien 7xa is mapped to FFxxx 
.equ sccbcmd,fi'7c00 
equ sccl>dta,h'7c01 
equ sccacmd,h'7c02 
equ sccadta,h'7c03 
.equ sccdcmd,fi'7c80 
equ sccddta,li'7c81 
.equ sccccmd,h'7c82 
equ scccdta,h'7c83 
equ pio,h'7d00 
equ Ied.l)'7d80 
equ io4,l)'7e00 
equ io5,h'7e80 
equ io6,h'7fCX) 
equ Io7,f)'7f80 

; Scroungemaster II minimal initialization. 

; Wtien tl<e SM II is powered up, the mapping RAM 

; is in an unknown state, so only the EPROM and 

: mapping RAM can l>e accessed. The first thing 

: we must do is put the mapping RAM in a known 

; state. This mapping will make the on-t>oard I/O 

: accessible. No matter what RAM chip is 

: installed, 7K of RAM will be available from 

; program addresses EOOO to 7BFF Remember that 

: the mapping values are k>gk»lly Inverted by 

; the mapping RAM. 




sU h'fOOO 


sta h'eOOO 


sta h'dOCO 


sta h'cOOO 


sta h'bOOO 


sta h'aOOO 


; map 7)oa -> FFxxx 
;(on-board RAM & I/O) 
; map 6xxx -> FExxx 
;(on-board RAM) 
i map 5xxx -> FDxxx 

; map 4xxx -> FCxxx 

; map 3xxx -> FBxxx 

; map 2xxx -> FAxxx 

sta h'9000 ; map 1xxx-> F9xxx 


sta h'8000 ; map Oxxx -> F8xxx 

; A simple loop to output 00->FF to LEDs, 
, virithout using any RAM. Remember that 
: the LEDs will appear k>gically inverted 
;n- = off, tr^on). 


leax 1 ,x 
bne tkx}p 
stb led 
bne tloop 

; increment counter lo 16 

; increment counter hi 8 
; output to LEDs 

Initialize one Zilog SCC. Subroutines 
require the use of the stack, so this 
needs RAM. Also note that some common 
sec registers are set up in the port A 
table, and some in the port B table, so 
you need to initialize BOTH ports. 

Ids #endram 
Idx #sccatbl 
jsr sccinit 
Mx #sccbtbl 
jsr sccinit 

point stack to RAM top 
pott A setup table 
common init routine 
port B setup table 
common init routine 

; A simple kx>p to receive a character, 

; output it to the LEDs, increment it, 

; and output it to the serial port. We 

; know that by the time one character is 

; received, the transmitter will be ready 

; to send one character 

qk>op: kJb sccacmd ; wait for n< char avail. 


beq qloop 

Idb sccadta ; input char from sec 

stb led ; output char to led 


stb sccadta ; output char+1 to sec 

bra qloop 

Zilog SCC initialization routine, 
entered with table address in X. 
You can use this routine in your own 

sccinit; Idy ,x++ 

Idb ,x+ 

sccloop: Ida ,%* 

sta ,y 

get see port address 
get # of bytes to output 
get byte from table 
store to SCC port 


bne secloop 


.dw seeacmd 









































dw sccbemd 





































port address 

37 bytes follow 

just in case, reset reg ptr 

hardware reset irpts tyFf 

16xclock,async,1 stop.nopar. 

no dma, all Irpts disabled 

irpt vector (for future use) 

rx 8 bits, rx disabled 

tx 8 bits, tx disabld. RTSA hi 

status low, ir^ off 

nrz encoding 

no xtal, BRG->rxc txc, TRxC in 

BRG lo byte • 4800 baud at 16x 

hi byte - w/ 4 MHz BRG elk 

DTR pgm'd, BRG from PCLK 

as above, plus BRG enabled 

as above, plus nc enabled 

as above, plus b( enabled 

no ext/sts inten-upts 

reset ext/sts interrupts twice 

no dn)a. all irpts disabled 

port address 
31 bytes follow 
just in case, reset reg p^ 
16xclock,async,1 stop, no par. 
no dma, all irpts disabled 
rx 8 bits, rx disabled 
tx 8 bits, b( disabld, RTSB hi 
nrz encoding 

no xtal, BRG->rxc txc, TRxC in 
BRG k> byte - 4800 baud at 16x 
hi byte - w/ 4 MHz BRG elk 
DTR pgm'd, BRG from PCLK 
as above, plus BRG enabled 
as above, plus nc enabled 
as above, plus bt enabled 
no ext/sts interrupts 
reset ext/sts interrupts tv^ce 
no dma, all irpts disabled 
as above, plus irpt master enable 

The Computer Journal / #70 



The Computer Journal / #70 





ami I ton. Ontario 




Document Number 

Hai^ 16,' i'9^'4|ghee t'"' 

The Computer Journal / #70 


Regular Feature 
Group Reviews 


TCJ Staff Contacts 

TCJ Editor: Bill D. Kibler, PO Box 535, Lincoln, CA 95648, (916)645- 
1670, GEnie: B.Kibler, CompuServe: 71563,2243, E-mail: 

Z-System Support: Jay Sage,1435 Centre St. Newton Centre, MA 
02159-2469, (617)965-3552, BBS: (617)965-7259; E-mail; Also sells Z-System software. 

32Bit Support: Rick Rodman, BBS :(703)33 0-9049 (eves), E-mail: 
rickr@ virtech . . 

Kaypro Support: Charles Stafford, 4000 Norris Ave., Sacramento, 
CA 95821, (916)483-0312 (eves). Also sells Kaypro upgrades, see 
ad inside back cover. CompuServe 73664,2470 (73664. 2470@cis). 

S-100 Support: Herb Johnson, CN 5256 #105, Princeton, NJ 08543, 
(609)771-1503. Also sells used S-100 boards and systems, see inside 
back cover. 

6800/6809 Support: Ronald Anderson, 3540 Sturbridge Ct., Ann 
Arbor, MI 48105. 

Regular Contributors: 

Dave Baldwin, Voice/FAX (916)722-3877, or DIBs BBS (916) 722- 
5799 (use "computer", "journal", pswd "subscriber" as log on), 
Internet, CompuServe 70403,2444. 

Brad Rodriguez3ox 77, McMaster Univ., 1280 Main St. West, 
Hamilton, ONT, L8S ICO, Canada, Genie: B.Rodrigue22, E-mail: 

Frank Sergeant, 809 W. San Antonio St., San Marcos, TX 78666, E- 

Tilmann Reh, Germany, E-mail: 
Has many programs for CP/M+ and is active with Zl 80/280 ECB 
bus/Modular/Embedded computers. USA contact Jay Sage. 

Helmut Jungkunz, Munich, Germany, ZNODE #51, 8N1, 300-14.4, 
+49.89.9614574, or CompuServe 100024,1545. 

Ron Mitchell, Apt 1 107, 210 Gloucester St., Ottawa Ontario, Canada, 
K2P 2K4. GEnie- as R.MitchelB 1 , or CompuServe 70323,2267. 


Connecticut CP/M Users Group, contact Stephen Griswold, PO Box 
74, Canton CT 06019-0074, BBS: (203)665-1100. Sponsors East 
Coast Z-fests. 

Sacramento Microcomputer Users Group, PO Box 161513, Sacra- 

mento, CA 95816-1513, BBS: (916)372-3646. Publishes newsletter, 
$15.00 membership, meetings at SMUD 6201 S st., Sacramento CA. 

CAPDUG: The Capital Area Public Domain Users Group, Newslet- 
ter S20, Al Siegel Associates, Inc., PO Box 34667, Betherda MD 
20827. BBS (301) 292-7955. 

NOVAOUG: The Northern Virginia Osborne Users Group, Newslet- 
ter $12, Robert L. Critics, 7512 Fairwood Lane, Falls Church, VA 
22046. Info (703) 534-1186, BBS use CAPDUG's. 

The Windsor Bulletin Board Users' Group: England, Contact Rodney 
Hannis, 34 Falmouth Road, Reading, RG2 8QR, or Mark Minting, 
94 Undley Common, Lakenheath, Brandon, Suffolk, IP27 9BZ, Phone 
0842-860469 (also sells NZCOM/Z3PLUS). 

L.I.S.T.: Long Island Sinclair and Timex support group, contact 
Harvey Rait, 5 Peri Lane, Valley Stream, NY 11581. 

ADAM-Link User's Group, Sah Lake City, Utah, BBS: (801)484- 
5114. Supporting Coleco ADAM machines, with Newsletter and 

Adam International Media, Adam's House, Route 2, Box 2756, 
1829-1 County Rd. 130, Pearland TX 77581-9503, (713)482-5040. 
Contact Terry R. Fowler for information. 

AUGER, Emerald Coast ADAM Users Group, PO Box 4934, Fort 
Walton Beach FL 32549-4934, (904)244-1516. Contact Norman J. 
Deere, treasurer and editor for pricing and newsletter information. 

MOAUG, Metro Orlando Adam Users Group, Contact James Poulin, 
1146 Manatee Dr. Rockledge FL 32955, (407)631-0958. 

Metro Toronto Adam Group, Box 165, 260 Adelaide St. E., Toronto, 
ONT M5A INO, Canada, (416)424-1352. 

Omaha ADAM Users Club, Contact Norman R. Castro, 809 W. 33rd 
Ave. Bellevue NE 68005, (402)291-4405. Suppose to be oldest 
ADAM group. 

Vancouver Island Senior ADAMphiles, AD VISA newsletter by David 
Cobley, 17885 Berwick Rd. Qualicum Beach, B.C., Canada V9K 
1N7, (604)752-1984. 

Northern Illiana ADAMS User's Group, 9389 Bay Colony Dr. #3E, 
Des Plaines IL 60016, (708)296-0675. 

San Diego OS-9 Users Group, Contact Warren Hrach (619)221- 
8246, BBS: (619)224-4878. 

ACCESS, PO Box 1354, Sacramento, CA 95812, Contact Bob Drews 
(916)423-1573. Meets first Thurdays at SMUD 59Th St. (ed. bldg). 


The Computer Journal / #70 

Forth Interest Group, PO Box 2154, Oakland CA 94621 510-89- 
FORTH. International support of the Forth language. Contact for list 
of local chapters. 

The Pacific Northwest Heath Users Group, contact Jim Moore, PO 
Box 9223, Seattle, WA 98109-0223, 

The SNO-KING Kaypro User Group, contact Donald Anderson, 
13227 2nd Ave South, Burien, WA 98168-2637. 

SeaFOG (Seattle FOG User's Group, Formerly Osborne Users Group) 
PO Box 12214, Seattle, WA 98102-0214. 


The Z-Letter, supporting Z-System and CP/M users. David A.J, 
McGlone, Lambda Software Publishing, 149 West Hillard Lane, 
Eugene, OR 97404-3057, (503)688-3563, Bi-Monthly user oriented 
newsletter (20 pages+). Also sells CP/M Boot disks, software. 

The Analytical Engine, by the Computer History Association of 
California, 1001 Elm Ct. El Cerrito, CA 94530-2602. A ASCH text 
file distributed by Internet, issue #1 was July 1993. E-mail; 
kcrosby@crayola. win . net. 

Z-100 Lifeline, Steven W. Vagts, 2409 Riddick Rd, Elizabeth City, 
NC 27909, (919)338-8302. Publication for Z-100 (a S-100 machine). 

The Staunch 8/89'er, Kirk L. Thompson editor, PO Box 548, West 
Branch lA 52358, (319)643-7136. $15/yr(US) publication for H-8/ 

Sydex, PO Box 5700, Eugene OR 97405, (503)683-6033, Sells 
several CP/M programs for use with PC Clones ('22Disk' format/ 
copies CP/M disks using PC files system). 

Elliam Associates, PO Box 2664, Atascadero CA 93423, (805)466- 
8440. Sells CP/M user group disks and Amstrad PCW products. See 
ad inside back cover. 

Discus Distribution Services, Inc. sells CP/M for $150, CBASIC 
$600, Fortran-77 $350, Pascal/MT+ $600. 8020 San Miguel Canyon 
Rd., Salinas CA 93907, (408)663-6966. 

Microcomputer Mail-Order Library of books, manuals, and periodi- 
cals in general and H/Zenith in particular. Borrow items for small 
fees. Contact Lee Hart, 4209 France Ave. North, Robbinsdale MN 
55422, (612)533-3226. 

Star-K Software Systems Corp. PO Box 209, Mt. Kisco, NY 10549, 
(914)241-0287, BBS: (914)241-3307. 6809/68000 operating system 
and software. Some educational products, call for catalog. 

Peripheral Technology, 1250 E. Piedmont Rd., Marietta, GA 30067, 
(404)973-2156. 6809/68000 single board system. 68K ISA bus com- 
patible system. See inside front cover. 

Hazelwood Computers, RR# 1 , Box 36, Hwy 94@Bluffton, Rhineland, 
MO 65069, (314)236-4372. Some SS-50 6809 boards and new 
68000 systems. 

AAA Chicago Computers, Jerry Koppel, (708)681-3782. SS-50 6809 
boards and systems. Very limited quanity, call for information. 

The SEBHC Journal, Leonard Geisler, 895 Starwick Dr., Ann Arbor 
MI 48105, (313)662-0750. Magazine of the Society of Eight-Bit 
Heath computerists, H-8 and H-89 support. 

Sanyo PC Hackers Newsletter, Victor R. Frank editor, 12450 Skyline 
Blvd. Woodside, CA 94062-4541, (415)851-7031. Support for or- 
phaned Sanyo computers and software. 

the world of 68' micros, by FARNA Systems, PO Box 321, Warner 
Robins, GA 31099-0321. E-mail: New maga- 
zine for support of old CoCo's and other 68xx(x) systems. 

Amstrad PCW SIG, newsletter by Al Warsh, 2751 Reche Cyn Rd. 
#93, Colton, CA 92324. $9 for 6 bi-monthly newsletters on Amstrad 
CP/M machines. 

Historically Brewed, A publication of the Historical Computer Soci- 
ety. Bimonthly at $18 a year. HCS, 2962 Park Street #1, Jackson- 
ville, FL 32205. Editor David Greelish. Computer History and more. 

IQLR (International QL Report), contact Bob Dyl, 15 Kilburn Ct, 
Newport, RI 02840. Subscription is $20 per year. 

Update Magazine, PO Box 1095, Peru, IN 46970, Subs $18 per year, 
supports Sinclair, Timex, and Cambridge computers. 

Other Support Businesses 

Hal Bower writes, sells, and supports B/PBios for Ampro, SB 180, 
and YASBEC. $69.95. Hal Bower, 7914 Redglobe Ct., Severn MD 
21144-1048, (410)551-5922. 

MicroSolutions Computer Products, 132 W. Lincoln Hwy, DeKalb, 
IL 60115, (815)756-3411. Make disk copying program for CP/M 
systems, that runs on CP/M sytems, UN IF ROM Format-translation. 
Also PC/Z80 CompatiCard and UniDos products. 

GIMIX/OS-9, GMX, 3223 Arnold Lane, Northbrook, IL 60062, 
(800)559-0909, (708)559-0909, FAX (708)559-0942. Repair and 
support of new and old 6800/6809/68K/SS-50 systems. 

n/SYSTEMS, Terry Hazen, 21460 Bear Creek Rd, Los Gatos CA 
95030-9429, (408)354-7188, sells and supports the MDISK add-on 
RAM disk for the Ampro LB. PCB $29, assembled PCB $129, 
includes driver software, manual. 

Corvatek, 561 N.W. Van Buren St. Corvallis OR 97330, (503)752- 
4833. PC style to serial keyboard adapter for Xerox, Kaypros, Franklin, 
Apples, $129. Other models supported. 

Morgan, Thielmann & Associates services NON-PC compatible 
computers including CP/M as well as clones. Call Jerry Davis for 
more infomiation (408) 972-1965. 

Jim S. Thale Jr., 1150 Somerset Ave., Deerfield IL 60015-2944, 
(708)948-5731. Sells I/O board for YASBEC. Adds HD drives, 2 
serial, 2 parallel ports. Partial kit $150, complete kit $210. 

Trio Comapny of Cheektowaga, Ltd., PO Box 594, Cheektowaga NY 
14225, (716)892-9630. Sells CP/M (& PC) packages: InfoStar 1.5 
($160); SuperSort 1.6 ($130), and WordStar 4.0 ($130). 

Parts is Parts, Mike Zinkow, 137 Barkley Ave., Clifton NJ 07011- 
3244, (201)340-7333. Supports Zenith Z-100 with parts and service. 

The Computer Journal / #70 


The Computer Journal 

Back Issues 

Sales iimited to supplies in stock. 

Volume Number 1: 

• Issues 1 to 9 

• Serial Interfacing and Modem transfers 

• Floppy disk formats, Print spooler. 

• Adding 8067 Math Chip. Fitwr optics 

- 5-100 HI-RES graphics. 

• Controlling OC motors, Multi-user 

• VIC-20 EPROM Programmer, CP/M 3.0. 

• CP/M user functions and integration. 

Volume Numt>er 2: 

• Issues 1 to 1 9 

• Forth tutorial and Write Your Own. 
•68006 CPU for S-1 00. 

• RPM vs CP/M, BIOS Enhancements. 

• Poor Man's Distributed Processing. 

• Controlling Apple Stepper Motors. 

• Facsimile Pictures on a Micro. 

• Memory Mapped I/O on a ZX81 . 

Volume Number 3: 

• Issues 20 to 25 

• Designing an 8035 SBC 

• Using Apple Graphics from CP/M 

• Soldering & Ottier Strange Tales 

• Build an S-100 Floppy Disk Controller: 
WD2797 Controller for CP/M 68K 

- Extending Turix) Pascal: series 

• Unsoldering. The Arcane Art 

■ Analog Data Acquisition & Control: 
Connecting Your Computer to the Real 

• Programming the 8035 SBC 

- NEW-DOS: series 

• Variability in the BDS C Standard Library 

• The SCSI Interface: series 

• Using Turbo Pascal ISAM Files 

■ The Ampro Little Board Column: series 

• C Column: series 

■ The Z Column: series 

• The SCSI Interface: Introduction to SCSI 

• Editing the CP/M Operatir>g System 

• INDEXER: Turbo Pascal Program to Create 
an Index 

• Selecting & Building a System 

• Introduction to Assemble Code for CP/M 

• Ampro 186 Column 

• ZTime-1: A Real Time Clock for the Ampro 
Z-8Q Little Board 

Volume Numt>er4: 

• Issues 26 to 31 

• Bus Systertts: Selecting a System Bus 

■ Using the SB180 Real Tinne Clock 

- The SCSI Interface: Software for the SCSI 

• Inside Ampro Computers 

• NEW-DOS: The CCP Commands 

• ZSIG Comer 

• Affordable C Compilers 

• Concurrent Multitasking: A Review of 

• 68000 TinyGiant: Hawthorne's Low Cost 
16-brt SBC and Operating System 

■ The Art of Source Code Generation: 
Disassembling Z-80 Software 

• Feedback Control System Analysis: Using 
Root Locus Analysis & Feedback Loop 

• The C Column: A Graphics Primitive 

• The Hitachi HD64180: New Life for 8-bit 

• ZSIG Comer: Command Line Generators 
and Aliases 

• A Tutor Program in Forth: Writing a Forth 
Tutor in Forth 

• Disk Parameters: Modifying the CP/M Disk 
Parameter Block for Foreign Disk Formats 

• Starting Your Own BBS 

• Build an A/D Converter for the Ampro Little 

• HD64180: Setting the Wait States & RAM 
Refresh using PRT & DMA 

• Using SCSI for Real Time Control 

• Open Letter to STD Bus Manufacturers 

• Patching Turbo Pascal 

■ Choosing a Language for Machine Control 

■ Better Software Filter Design 

• MDISK Adding a 1 Meg RAM Disk to 
Ampro Little Board, Part 1 

• Using the Hitachi hd64180: Embedded 
Processor Design 

• 68000: Why use a new OS and the 68000? 

• Detecting the 8087 Math Chip 

• Floppy Disk Track Structure 

• Double Density Floppy Controller 

• ZCPR3 top for the Ampro Little Board 

• 3200 Hackers' Language 

• MDISK: Adding a 1 Meg RAM Disk to 
Ampro Little Board. Part 2 

• Non-Preemptive Multitasking 

• Software Timers for the 68000 

• Using SCSI for Generalized I/O 

• Communicating with Floppy Disks: Disk 
Parameters & their variations 

• XBIOS: A Replacement BIOS for the 

• K-OS ONE and the SAGE Demystifying 
Operating Systems 

• Remote: Designing a Remote System 

• The ZCPR3 Corner ARUN2 

Issue Number 32: 

- 1 5 copies now available - 

Issue Number 33: 

• Data File Conversion: Writing a Filter to 
Convert Foreign File Formats 

• Advanced CP/M: ZCPR3PLUS & How to 
Write Self Relocating Code 

• DataBase: The First in a Series on Data 
Bases and Information Processing 

• SCSI for the S-100 Bus: Another Example 
of SCSI's Versatility 

• A Mouse on any Hardware: Implementing 
the Mouse on a Z80 System 

• Systematic Elimination of MS-DOS Files: 
Part 2, Subdirectories & Extended DOS 

• ZCPR3 Corner: ARUNZ Shells & Patching 
WordStar 4.0 

Issue Number 34: 

• Developing a File Encryption System. 

• Datat>ase: A continuation of the data base 
primer series, 

• A Simple Multitasking Executive: Designing 
an embedded controller multitasking 

• ZCPR3: Relocatable code, PRL files, 
ZCPR34, and Type 4 programs. 

• New Microcontrollers Have Smarts: Chips 
with BASIC or Forth in ROM are easy to 

• Advanced CP/M. Operating system 
extensions to BOOS and BIOS, RSXs for CP/ 

• Macintosh Data File Conversion in Turbo 

Issue Number 36: 

• At! This & Modula-2: A Pascal-like 
alternative with scope and parameter passing. 

• A Short Course in Source Code Generation: 
Disassembling 8088 software to produce 
modifiable assem. source code. 

• Real Computing; The NS32032. 

• S-100: EPROM Bumer project for S-100 
hardware hackers. 

• Advanced CP/M: An up-to-date DOS, plus 
details on file structure and formats. 

• REL-Style Assembly Language for CP/M 
and Z-System, Part 1 : Selecting your 
assembler, linker and debugger. 

Issue Number 3€: 

• Information Engineering: Introduction. 

• Modula-2: A list of reference books. 

• Temperature Measurement & Control: 
Agricultural computer application. - 

• ZCPR3 Corner: Z-Nodes, Z-Plan, Amstrand 
computer, and ZFILE, 

• Real Computing: NS32032 hardware for 
experimenter, CPUs in series, software 

• SPRINT: A review 

• REL-Style Assembly Language for CP/M 
& ZSystems, part 2, 

■ Advanced CP/M Environmental 

Issue Numt>er 37: 

• C Pointers, Arrays & Structures Made 
Easier: Part 1, Pointers. 

• ZCPR3 Corner: Z-Nodes, patching for 

• Information Engineering: Basic Concepts 
fields, field definition, client worksheets 

• Shells: Using ZCPR3 named shell 
variables to store date variables 

• Resident Programs: A detailed look at 
TSRs & how they can lead to chaos 

• Advanced CP/M: Raw and cooked console 

• Real Computing: The NS 32000 

• ZSDOS: Anatomy of an Operating System: 

Issue Number 38: 

■ C Math: Handling Dollars and Cents With 

• Advanced CP/M: Batch Processing and a 

• C Pointers, Arrays & Structures Made 
Easier: Part 2, Arrays, 

• The Z-System Corner: Shells and 2EX, 
new Z-Node Central, system security under 

■ Information Engineering, The portable 
Information Age. 

• Computer Aided Publishing: Introduction to 
publishing and Desk Top Publishing. 

• Shells: ZEX and hard disk backups. 

• Real Computing: The National 
Semiconductor NS320XX. 

• ZSDOS: Anatomy of an Operating System, 
Part 2. 

Issue Number 39: 

• Programming for Performance: Assembly 
Language techniques. 

• Computer Aided Publishing: The Hewlett 
Packard LaserJet 

• The Z-System Corner System 
enhancements with NZCOM. 

• Generating LaserJet Fonts: A review of 

• Advanced CP/M: Making old programs Z- 
System aware. 

• C Pointers, Arrays & Structures Made 
Easier: Part 3: Structures. 

■ Shells: Using ARUNZ alias with ZCAL, 

• Real Computing: The National 
Semiconductor NS320XX, 

Issue Number 40: 

• Programming the LaserJet: Using the 
escape codes. 

• Beginning Forth Column: Introduction. 

• Advanced Forth Column: Variant Records 
and Modules. 

• LINKPRL: Generating the bit maps for PRL 
files from a REL file. 

• WordTech's dBXL: Writing your own 
custom designed business program. 

• Advanced CP/M: ZEX 5 0«The machine 
and the language. 

• Programming for Performance: Assembly 
language techniques. 

• Programming Input/Output With C 
Keyboard and screen functions. 

• The Z-System Corner: Remote access 
systems and BDS C. 

• Real Computing: The NS320XX 

Issue Number 41: 

• Forth Column: ADTs. Object Oriented 

• Improving the Ampro LB: Overcoming the 
88Mb hard drive limit. 

• How to add Data Structures in Forth 

• Advanced CP/M: CP/M is hacker's haven, 

and Z-System Command Scheduler. 

• The Z-System Corner: Extended Multiple 
Command Line, and aliases 

• Programming disk and printer functions 
with C 

• LINKPRL Making RSXes easy 

• SCOPY: Copying a series ot unrelated 

Issue Number 42: 

• Dynamic Memory Allocation Allocating 
memory at runtime with examples in Forth 

• Using BYE with NZCOM. 

• C and the MS-DOS Screen Character 

• Forth Column Lists and object oriented 

• The Z-System Corner: Genie, BDS Z and 
Z-System Fundamentals. 

• 68705 Emt)edded Controller Application: 
An example of a single-chip microcontroller 

■ Advanced CP/M: PiuPerfect Writer and 
using BDS C with REL files. 

• Real Computing: The NS 32000, 

Issue Number 43: 

• Standardize Your Floppy Disk Drives. 

• A New History Shell for ZSystem. 

■ Heath's HDOS. Then and Now 

• The ZSystem Corner: Software update 
service, and customizing NZCOM. 

• Graphics Programming With C Graphics 
routines for the IBM PC, and the Turbo C 
graphics library. 

• Lazy Evaluation End the evaluation as 
soon as the result is known. 

• S-100: There's still life in the old bus, 

• Advanced CP/M: Passing parameters, and 
complex error recovery. 

• Real Computing: The NS32000. 

Issue Number 44 ; 

■ Animation with Turbo C Part 1: The Basic 

• Multitasking in Forth: New Micros F68FC11 
and Max Forth 

• Mysteries of PC Floppy Disks Revealed: 
FM, MFM, and the twisted cable, 

• DosDisk: MS-DOS disk format emulator for 

• Advanced CP/M: ZMATE and using lookup 
and dispatch for passing parameters 

• Real Computing: The NS32000 

• Forth Column: Handling Strings. 

• Z-System Corner: MEX and telecommuni- 

Issue Number 45: 

• Embedded Systems for the Tenderfoot 
Getting started with the 8031 . 

• The Z-System Corner. Using scripts > 

• The Z-System and Turbo Pascal: P 
TURB0.COM to access the Z-System 

• Embedded Applications: Designing a Z80 
RS-232 communications gateway, part 1, 

• Advanced CP/M: String searches and 
tuning Jetfind. 

• Animation with Turbo C: Part 2, screen 

• Real Computing: The NS32000, 

Issue Number 46: 

• Build a Long Distance Printer Driver, 

• Using the 803rs built-in UART for serial 

• Foundational Modules in Modula 2, 

• The Z-System Corner: Patching The Word 
Plus spell checker, and the ZMATE macro 
text editor, 

• Animation with Turbo C: Text in the 
graphics mode, 

• Z80 Communications Gateway: 
Prototyping, Counter/Timers, and using the 
Z80 CTC 

Issue Number 47: 

• Controlling Stepper Motors with the 

• Z-System Come'" ZMATE Macro Language 

• Using 8031 Interrupts 

• T-1 : What it is & Why You [Meed to Know 

• ZCPR3 & Modula, Too 

• Tips on Using LCDs: Interfacing to the 

• Real Computing: Debugging, NS32 Multi- 
tasking & Distributed Systems 


The Computer Journal / #70 

• Long Distance Printer Driver: correction 

• ROBaSOG 90 

Issue Number 48: 

■ Fast Matti Using Logarithms 

• Forth and Forth Assembler 

• Moduia-2 and ttie TCAP 

• Adding a Bernoulli Drive to a CP/M 
Computer {Building a SCSI Interface) 

• Review of BDS "Z" 

• PMATE/ZMATE Macros, Pt 1 

• Real Computing 

• Z-System Comer: Patching MEX-Plus and 
TheWord, Using ZEX 

• Z-Best Software 

ssue Number 49: 

• Computer Network Power Protection 

• Floppy Disk Alignment w/RTXEB, Pt, 1 

• Motor Control vwth the F68HC1 1 

• Controlling Home Heating & Lighting, Pt, 1 

• Getting Started in Assembly Language 

• LAN Basics 

• PMATE/ZMATE Macros, Pt, 2 

• Real Computing 

■ Z-System Corner 

■ Z-6est Software 

ssue Number 50: 

• Offload a System CPU with the Z181 

• Floppy Disk Alignment w/RTXEB, Pt 2 

■ Motor Control »nth the F68HC1 1 

• Modula-2 and the Command Line 

• Controlling Home Heating & Lighting, Pt, 2 

• Getting Started in Assembly Language Pt 2 

• Local Area Networks 

• Using the ZCPR3 lOP 

• PMATE/ZMATE Macros, Pt 3 

• Z-System Corner, PCED 

• Z-Best Softvrare 

• Real Computing, 32FX1 6, Caches 

Issue Number S1: 

• Introducing the YASBEC 

• Floppy Disk Alignment w/RTXEB, Pt 3 

• High Speed Modems on Eight Bit Systems 

■ A Z8 Talker and Host 

• Local Area Networks — Ethernet 

• UNIX Connectivity on the Cheap 

• PC Hard Disk Partition Table 

■ A Short Introduction to Forth 

• Stepped Inference as a Technique for 
Intelligent Real-Time Embedded Control 

• Real Computing, the 32CG160, Swordfish, 
DOS Command Processor 


• Z-System Comer, The Trenton Festival 

• Z-Best Software, the Z3HELP System 

Issue Number 52: 

• YASBEC. The Hardware 

• An Arbitrary Wavefomn Generator, Pt. 1 

• B.Y.O. Assembler. in Forth 

• Getting Started in Assembly Language, Pt 3 

• The NZCOM lOP 

• Servos and the F68HC1 1 

• Z-System Corner, Programming for 

• Z-Best Softvrare 

• Real Computing, X10 Revisited 

The Computer Journal Back Issues 


• Controlling Home Heating & Lighting, Pt. 3 

■ The CPU280, A High Performance Single- 
Board Computer 

Issue Number 53: 
The CPU280 
■ Local Area Networks 
Am Arbitrary Waveform Generator 
Real Computing 
Zed Fest '91 
Z-System Corner 

Getting Started in Assembly Language 
Z-BEST Software 

Issue Number 54: 
- Z-System Corner 

B.Y.O. Assembler 

Local Area Netvrorks 

Advanced CP/M 

ZCPR on a 1 6-Bit Intel Platform 

■ Real Computing 
Interrupts and the Z80 

■ 8 MHZ on a Ampro 
Hardware Heavenn 

What Zilog never told you about the Supers 
An Arbitary Waveform Generator 
The Development of TDOS 

Issue Number 55: 
Fuzzilogy 101 

■ The Cyclic Redundancy Check in Forth 
The lnternetv«>rk Protocol (IP) 
Z-System Corner 

Hardware Heaven 
Real Computing 

Remapping Disk Drives through the Virtual 
The Bumbling Mathmatician 
Z-BEST Software 

Issue Number 56: 

TCJ - The Next Ten Years 

Input Expansion for 8031 

Connecting IDE Drives to 8-Bit Systems 

Real Computing 

8 Queens in Forth 

■ Z-System Corner 

- Kaypro-84 Direct File Transfers 
Analog Signal Generation 

Issue Number 57: 

Home Automation with XI 
File Transfer Protocols 
MDISK at 8 MHZ. 
Real Computing 

■ Shell Sort in Forth 

■ Z-System Corner 

■ Introduction to Forth 

■ DR. S-100 
Z AT Last! 

Issue Number 58: 
Multitasking Forth 
Computing Timer Values 
Affordable Development Tools 
Real Computing 
Z-System Corner 
Mr. Kaypro 
DR S-100 

Issue Number 59: 

Moving Forth 

Center Fold IMSAI MPU-A 
■ Developing Forth Applications 

Real Computing 

Z-System Corner 

Mr Kaypro Review 

DR. S-100 

Issue Number 60: 

Moving Forth Part II 
Center Fold IMSAI CPA 
Four for Forth 
Real Computing 
■ Debugging Forth 
Support Groups for Classics 
Z-System Corner 
Mr. Kaypro Review 
DR S-100 

Issue Number 61: 
Multiprocessing 6809 part I 
Center Fold XEROX 820 
Quality Control 
Real Computing 
Support Groups for Classics 
Z-System Corner 
Operating Systems - CP/M 
Mr. Kaypro 5MHZ 

Issue Number 62: 

SCSI EPROM Programmer 

Center Fold XEROX 820 

DR S-100 
• Real Computing 

■ Moving Forth part III 

■ Z-System Corner 
Programming the 6526 CIA 

■ Reminiscing and Musings 

■ Modem Scripts 

issue Number 63: 

SCSI EPROM Programmer part II 
Center Fold XEROX 820 
■DR S-100 
Real Computing 
Multiprocessing Part 11 
Z-System Corner 
6809 Operating Systems 
Reminiscing and Musings 
IDE Drives Part II 

Issue Number 64: 


Center Fold last XEROX 820 

DR S-100 

Real Computing 

Moving Forth Part IV 
Z-System Corner 
Small Systems 
Mr. Kaypro 
IDE Drives Part 111 

Issue Number 65: 

Small System Support 
Center Fold ZX80/81 
DR S-100 
Real Computing 
European Beat 
PC/XT Corner 
Little Circuits 
Levels of Forth 
Sinclair ZX81 

Issue Number 66: 
Small System Support 
Center Fold: Advent Decoder 
DR S-100 
Real Computing 
Connecting IDE Drives 
PC/XT Corner 
Little Circuits 
Multiprocessing Part III 
Z-System Corner 

Issue Number 67: 
Small System Support 
Center Fold: SS-50/SS-30 
DR S-100 
Real Computing 
Senal Kaypro Interrupts 
Little Circuits 
Moving Forth Part 5 
European Beat 

issue Number 68: 

Small System Support 
Center Fold: Pertec/Mits 4P10 
Z-System Corner 11 
Real Computing 
PC/XT Corner 
Little Circuits 

Multiprocessing Forth Part 4 
Mr Kaypro 

issue Number 69: 

Small System Support 
Center Fold: S-100IDE 
Z-System Corner 11 
Real Computing 
PC/XT Corner 
DR. S-100 
Moving Forth Part 6 
Mr. Kaypro 


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The Computer Journal / #70 


Regular Feature 
Editorial Comment 

The Computer Corner 

By Bill Kibler 

I m^ be behind in getting to projects for 
TCJ, but lots of fim things have been 
happening. At woric a few more unex- 
pected trips to the job site happened, but 
they should all be done for now. Since 
that project is done, others are popping 
up. One of which is determining how to 
sui^rt 8051 code. 

I would like to move to Forth based 
systems, as I feel the built in diagnostics 
would help resolve problems faster. The 
projects are already done in Intel 8051 
ASM. The Intel assembler has many 
features and options that more current 
versions have since dropped. We have 
tried a few newer assemblers, and even 
one IDE (integrated development Envi- 
rotunent - Turbo Pascal like edit/as- 
semble/run) on Windows. 

The results of testing indicate major 
editing would be needed of our older 
code for any of the newer assemblers. 
Why change then if the Intel version is 
working fine? The answer is not clear, 
but going to the IDE type of environ- 
ment is suppose to improve overall efiFi- 
ciency. I rather question that idea, but 
then people who have not done 15 years 
of assembly, might find the IDE faster 
and easier to use. 

There is no question that old style as- 
semblers require a bit more inside knowl- 
edge of DOS and BATCH file usage. I 
have set up several assembly develop- 
ment work groups using just BATCH 
files. What is needed is a major effort to 
arrange your sub directories such that 
you can divide files, functions, and his- 
tory files for easy manipulation by batch 
files. Of course the most important tool 
is not the assembler but a version control 

Version control allows tracking and back 
tracking of changes to the source file. 
What I find most people not doing 
enough of is archiving off their versions 
of work. Whatever you do, you should 
store off" your work both in archived 
areas of your disk, and on separate disks. 
You can buy version control programs 
that work very well for tracking when 
you reached this or that release stage. 
But simple archiving to other disks with 
clear labeling can work just fine, IDE's 
not having version control built in, are 
probably not worth considering. 

When I am working on something very 
important, I may have four or five floppy 
disks, along with several zipped files. 
This file system gives me both archive 
and safety of mind. A close fiiend just 
wasted 3 weeks recovering data from a 
non backed up crash. He had taped it 
some months before, but not that day the 
machine crashed. He now follows my 
lead and users both tape ( religiously) 
and floppy as well. With my system, the 
worse that could happen might be a few 
hours of lost work, easy to replace. 


Got two interesting items in the mail 
this week. From Lee Bradley I received 
the MY-Z-DEMO disk. Now Lee only 
charges $10 for this disk. That is really 
a great bargain, and only the CP/M CD 
ROM will have more information in one 
place (Beta CD ROM completed - mas- 
tering in process as of early Nov.) on 
ZCPR If you run a PC DOS machine 
this is the way to go. It is fast, already 
installed with Zsystem when un-zipped, 
comes with 22DSK, and 216 programs 
of mostly the "Z" type. 

I took it to work the other day and over 
lunch used it to copy Emmanuel Roche's 
QX-10 formatted disk, and then unpack 
them with the programs supplied as well. 
It was simple, painless, and fast to use. 
What always surprises me is that many 
of these programs are better than any of 
their equivalent in MSDOS. 

Now I know that Lee is not going to get 
rich on this, and in fact it really is just a 
service to help people get over the learn- 
ing curve with Zsystem. Because of that 
and the fact that he really does want you 
to send the authors of 22DSK and 
MYZ80 money if you start using the 
program, I think you should drop the 
tenner in the mail ASAP. Here is Lee's 
address: Lee Bradley, 24 East Cedar 
Street, Newington, CT 06111-2534, 

The other item of interest was a book on 
using 8052 BASIC. Being an editor and 
getting an occasional free book con^ 
with the duties. The few I get ar'^^ so 
much PC based and usually so bad I let 
the bugs have at them. The one from 
Lakeview Research was different for a 
change. It is a book our readers can 
probably understand and actually make 
use of 

I am not high on doing BASIC with 
8051 or 8052's, but then I passed the 
beginner stage too long ago to remem- 
ber. Jan Axelson, a writer for our com- 
petitors The Microcomputer Journal 
(names seems a bit familiar doesn't it.) 
has a good writing style and a strong 
grasp of getting beginners going. 

The book, "The Microcontroller Idea 
Book" has about 270 pages of good size 
text and schematics of projects that 
should help you understand embedded 


The Computer Journal / #70 

system without too much fuss. The top- 
ics are relevant and the BASIC code 
should have you paying more attention 
to the hardware or project than getting 
lost in assembly coding. Price is $31.95, 
plus $3.00 shipping from Lakeview Re- 
search, 2209 Winnebago St. Madison, 
WI 53704 (608) 241-5824. 

One fact I picked out of Jan's book was 
BASIC being available in source form. 
In chapter 14 she talks about using ex- 
ternal memory to run BASIC and ex- 
plains how you can extend the BASIC in 
your own ROM. She states that Intel and 
Phillips BBS's have the assembly source 
and some vendors like Iota Systems have 
products with their extensions added to 
that source. 

Since one of TCTs reluctance to use 
BASIC was lack of uniform source code, 
maybe here is an answer. Get the source 
from the BBS's and adapt it to Z80/ 
6809/6800/??? systems. That would give 
us common code across 8051 to Z80 or 
more. Might entail some work replacing 
some smaller systems current BASIC, 
but then the user would have the source, 
which most don't have now. Sounds like 
an area the look fiirther into to me. 

And look I did the other day. On AMR's 
BBS I found the Intel version and two 
other. One looks a little smaller than the 
8052, because it is for 805 1 's. The other 
is a version of Tiny Basic. Now Tiny 
Basic is a bit like Small C in that many 
versions have already been done for most 
CPU types. I believe I have a 68000 
version aroimd somewhere, and reason- 
ably sure I have seen a Z80 version as 
well. This ROMable version has many 
good features and with source might be 
adaptable to all small systems. Think 
about it. 

Buy the way, Jan's book has many sec- 
tions you might find famiUar if you sub- 
scribe to the TMCJ. It also made me 
consider one area not yet in CD ROM, 
embedded support. I have yet to see a 
CD ROM that is devoted entirely to sup- 
porting smaller systems. The Source CDs 
have all the cross assemblers and a few 
utilities, but no actual 8051 programs. I 
know that Motorola has the old 6800 
users group programs on their BBS. But 

that material is many years old now, and 
yet 6805 or 681 1 code samples are float- 
ing all around. Maybe I can twist the 
Walnut Creek people to do one, only a 
bit faster since embedded markets are 
moving faster than CP/M. 

40MHZ Z80 

I got my copies of the latest information 
from Zilog. A bit confiising and yet very 
amazing as well. One of the sheets was 
on the new Z380, with 4 sets of 32 bit 
Z80 compatible registers. 32 Bit address- 
ing, 16 bit data paths, DRAM refresh 
controller built in. 100 pin package, with 
25 MHZ speeds at 3 volts and 40 MHZ 
at 5 volts, wow. 

Another booklet lists all the major Z80 
related variations ZILOG produces. A 
rather good cross sample of integrated 
devices that should fill any application 
you might meet. I zeroed in on the em- 
bedded controllers to find the Z80L180 
with a 33MHZ speed listed (at 3.3 volts). 
The same page shows the Z80380 with 
a 18 MHZ speed rating. The results is 
some leg pulling here, but in which di- 
rection I am not sure. I checked dates to 
see if one was a pre release, but none to 
be found. 

One other device to catch my eye, was 
the Z85C80, which contains the 85C30 
sec (Serial Communications Control- 
ler - two serial ports) and the 53C80 
SCSI controller in one package. Also 
some math chips that might make a great 
Forth engine at 40 MHZ (Z86I93). I 
need to comment again, the speeds 
seemed to vary in this flyer a bit more 
than made sense. But high or lower, the 
selection is great and I hope the new 
Z380 might get more interest started in 
Z80's again, this time from the embed- 
ded people. Only time will tell. 

Till Next Time.. 

Until the next issue and next year, please 
keep the letters coming and let me know 
if there is some direction not supported 
you need help on. Till then, keep hack- 

MYZ80 DEMO files list: -DEMO.OOl, - 




FATCAT3.002, FATCAT3.003, FATCAT3.004, 








The Computer Journal / #70 




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